The Doctor is the central character in the long-running BBC television science-fiction series Doctor Who, and also features in a vast range of spin-off novels, audio dramas and comic strips connected to the series.
To date, ten actors have officially played the role in the television series (including the 1996 television film), with these changes being explained by his ability to regenerate. Several other actors have played the character on stage and film, in audio dramas, and in occasional special episodes of the series. The character's enduring popularity led the Daily Telegraph to dub him "Britain's favourite alien".
The Doctor explores the universe at random, using his extensive knowledge of science, technology and history (from his perspective) to avert whatever crises he encounters. The imprecise nature of his travels is initially attributed to the age and unreliability of the TARDIS's navigation system. However, after his trial and restriction to late twentieth century Earth, he demonstrates the ability to reach a destination of his own choosing more often than not. In the last episode of series 4 in the revived series (2008) "Journey's End", the Doctor states that the reason for the previous bumpy navigation was that the TARDIS is meant to have six pilots. The Doctor generally travels with one or more companions. Most of these make a conscious decision to travel with him, but others, especially early in the series, are accidental passengers.
The character of the Doctor was created by the BBC's Head of Drama Sydney Newman. The first format document for the series that was to become Doctor Who — then provisionally titled The Troubleshooters — was written up in March 1963 by C. E. Webber, a BBC staff writer who had been brought in to help develop the project. Webber's document contained a main character described as "The maturer man, 35–40, with some 'character twist'." However, Newman was not keen on this idea and — along with several other changes to Webber's initial format — created an alternative lead character named "Dr Who": a crotchety older man piloting a stolen time machine, on the run from his own far future world. No written record of Newman's conveyance of these ideas — believed to have taken place in April 1963 — exists, and the character of "Dr Who" first begins appearing in existing documentation from May of that year.
The character was first portrayed by William Hartnell in 1963. When, after three years, Hartnell left the series due to ill health, the role was handed over to respected character actor Patrick Troughton. To date, official television productions have depicted ten distinct incarnations of the Doctor (due to Hartnell's death in 1975, actor Richard Hurndall substituted in his role as the First Doctor in 1983's The Five Doctors, resulting in a technical total of eleven actors). Of those, the longest-lasting incarnation is the Fourth Doctor, as played by Tom Baker. Currently, the Tenth Doctor is portrayed by David Tennant.
At the series' beginning, nothing at all is known of the Doctor: not even his name, the actual form of which remains a mystery. In the very first serial, An Unearthly Child, two teachers from Coal Hill School in London, Barbara Wright and Ian Chesterton, become intrigued by one of their students, Susan Foreman, who exhibits high intelligence and unusually advanced knowledge. Trailing her to a junkyard at 76 Totter's Lane, they encounter a strange old man and hear Susan's voice coming from inside what appears to be a police box. Pushing their way inside, the two find that the exterior is actually camouflage for the dimensionally transcendental interior of the TARDIS. The old man, whom Susan calls "Grandfather" but who identifies himself as "the Doctor", subsequently kidnaps Barbara and Ian to prevent them from telling anyone about the existence of the ship, taking them on an adventure in time and space.
As a time traveller, the Doctor has been present at or directly involved in countless major historical events on the planet Earth and elsewhere — sometimes more than once. In the 2005 series premiere, "Rose", it is revealed that the Ninth Doctor was instrumental in preventing a family from boarding the Titanic prior to her fateful voyage. In "The End of the World", the Doctor claimed to have been on board and survived the Titanic's sinking to find himself 'clinging to an iceberg.' The Fourth Doctor also mentioned this event in Robot and The Invasion of Time, where he claims the sinking was not his fault.
Many historical figures on Earth have also encountered the Doctor. In City of Death it is revealed that the Doctor has met Leonardo da Vinci and William Shakespeare (whom he re-met in "The Shakespeare Code"), and that the first folio of the latter's Hamlet was transcribed by the Doctor himself (City of Death). He has also met a young H. G. Wells (Timelash), Albert Einstein (Time and the Rani), Mao Tse Tung (The Mind of Evil), Richard the Lionheart (The Crusade), Wyatt Earp (The Gunfighters) and Marco Polo (Marco Polo). More recently, the Doctor has shared adventures with Charles Dickens ("The Unquiet Dead"), Agatha Christie ("The Unicorn and the Wasp"), Queen Victoria ("Tooth and Claw"), and Madame de Pompadour ("The Girl in the Fireplace"). A photograph seen in the 2005 series shows that the Ninth Doctor witnessed the death of US president John F. Kennedy. In the episode ("Gridlock") after handing his coat to Brannigan and his wife he asks them to take care of it saying "Janis Joplin gave me that coat."
It is this penchant for becoming "involved" with the universe — in direct violation of official Time Lord policy — that has caused the Doctor to be labelled a renegade by the Time Lords. Most of the time, however, his actions are tolerated, especially given that he has saved not just Gallifrey but also the universe several times over. The Time Lords are also partial to sending him on missions when deniability or expendability is needed. The Doctor's standing in Time Lord society has waxed and waned over the years, from being a hunted man to being appointed Lord President of the High Council. He does not assume the office for very long, and is eventually removed from it in his absence.
By the time of his ninth incarnation, the Doctor believes himself to be the last surviving Time Lord following the Last Great Time War, although he learns in his tenth incarnation that the Master also survived ("Utopia"). Despite the Doctor's desperate attempts to save the Master from his evil ways, the Master is shot by his wife and refuses to regenerate, seemingly leaving the Doctor alone once more ("Last of the Time Lords"). However, the final scenes involving the Master's body leave the possibility of a future return open.
In his final serial, the Second Doctor states that Time Lords can live forever, "barring accidents." When "accidents" do occur, Time Lords can usually regenerate into a new body, however it is stated in The Deadly Assassin that Time Lords can only regenerate a total of twelve times.
In the first episode, Barbara addresses the Doctor as "Doctor Foreman", as this is the surname the Doctor's granddaughter Susan goes by, and the junkyard in which they find him bears the sign "I.M. Foreman". When addressed by Ian with this name in the next episode, the Doctor responds, "Eh? Doctor who? What's he talking about?" Later, when he realises that "Foreman" is not the Doctor's name, Ian asks Barbara, "Who is he? Doctor who?" (In an ultimately-unused idea from documents written at the series' inception, Barbara and Ian would have subsequently referred to the Doctor as 'Dr. Who', given their not knowing his real given name.)
Similarly, in the 2005 series premiere "Rose", when asked his name, the Doctor replies, "Just 'The Doctor'." New companion Rose Tyler later finds a website devoted to the Doctor on the Internet, run by a conspiracy theorist who has been tracking the Ninth Doctor's appearances throughout history, carrying the title "DOCTOR WHO?" (see Doctor Who tie-in websites). The BBC launched a "real" version of this website with the idea that it is run by Mickey Smith, Rose's boyfriend (having taken over the site following the death of its originator).
In "The Empty Child" (2005), for want of a better name Rose introduces the Doctor to Jack Harkness as "Mr. Spock". (According to the DVD commentary for this episode, the Doctor was originally to have responded "I'd rather have 'Doctor Who' than Star Trek".)
Although listed in the on-screen credits for nearly twenty years as "Doctor Who" or "Dr Who", the Doctor is never really called by that name in the series, except in a tongue-in-cheek manner; for example, in The Five Doctors when one character refers to him as "the Doctor", another character asks, "Who?" The only real exception is the computer WOTAN in the serial The War Machines, which commands that "Doctor Who is required." The Third Doctor's car, dubbed "Bessie", carried the licence plate WHO 1, the only ongoing reference to the "Doctor Who" enigma in the original series. The Third Doctor also later drove an outlandish vehicle called the "Whomobile" in publicity materials, but it is never referred to as such in the series, being simply known as "the Doctor's car". The name "Doctor Who" is also used in the title of the serial Doctor Who and the Silurians, but this was a captioning mistake and not an in-story mention. The only other time this occurs is in the title of Episode 5 of The Chase: "The Death of Doctor Who".
In the Third Doctor serial The Dæmons the Doctor is briefly given the alias of the Great Wizard Qui Quae Quod. This is actually the masculine, feminine and neuter forms of the interrogative "who" in the Latin language.
In "The Christmas Invasion", the newly regenerated Doctor stumbles out of the TARDIS in a confused state in front of Jackie Tyler and Mickey. When Rose emerges from the TARDIS, she tells them that he is the doctor to which a confused Jackie replies "What do you mean that's the doctor? Doctor Who?". In "The Girl in the Fireplace" (2006), Madame de Pompadour reads the Doctor's mind and remarks about his name, "Doctor who? It's more than just a secret, isn't it?" In the podcast commentary on the BBC website, writer Steven Moffat suggests that, as the Doctor does not tell even his closest companions his name, there must be a "dreadful secret" about it. Within the same commentary, Moffat and actor Noel Clarke jokingly suggest his name to be "Curtis". Ironically, according to the in-vision commentary on the DVD release, David Tennant had to inform actress Sophia Myles (who played Madame de Pompadour) that she was not, in fact, revealing the Doctor's surname as she believed was the intent of the dialogue. In "The Shakespeare Code", the Carrionite Lilith, unable to discover his true name, remarks, "Why would a man hide his title in such despair?" A psychically-inspired human in "The Fires of Pompeii" remarks that his name Doctor is "false" and that his "true name" is in fact "hidden". In Moffat's "Forest of the Dead", the character River Song reveals she knows the Doctor in his future, and it is implied that they shared a very intimate relationship. In order to gain his trust, she whispers something—inaudible to the audience—into his ear, which he later reveals was his real name. The Doctor states that there is "only one reason" he would reveal his name and that there is "only one time [he] could."
Doctor Who spin-off media, which are of uncertain canonicity, have suggested that the character uses the name "the Doctor" because his actual name is impossible for humans to pronounce. This is also repeated by companion Peri Brown in the radio serial Slipback. This is unlikely to be true, since River Song whispers it to him in "Forest of the Dead." The Faction Paradox encyclopedia The Book of the War, which is of dubious canonicity, states that all renegades from the Homeworld/Gallifrey abandon their names to symbolise how they leave their culture.
The character played by Peter Cushing in the films Dr. Who and the Daleks and Daleks - Invasion Earth 2150 AD referred to himself as "Dr. Who". However, these films are not considered part of the canon as they were based upon already-televised adventures featuring William Hartnell and made considerable alterations to the characters of the Doctor and his companions.
The Telos novella Frayed by Tara Samms (which takes place prior to "An Unearthly Child") has the First Doctor being given that title by the staff of a besieged human medical facility on the planet Iwa, suggesting at the end that the Doctor liked the official title so much that he adopted it. However, this does not quite explain why the Time Lords use the same title in addressing him. The same story also has Jill, a young girl living in the facility, naming the Doctor's granddaughter "Susan" after Jill's mother. The canonicity of all non-television sources is uncertain.
To make up for his lack of a practical name, the Doctor often relies upon convenient pseudonyms. In The Gunfighters, the First Doctor uses the alias Dr. Caligari. In The Highlanders the Second Doctor assumes the name of "Doctor von Wer" (a German approximation of "Doctor Who"), and signs himself as "Dr. W" in The Underwater Menace. In The Wheel in Space, his companion Jamie McCrimmon, reading the name off some medical equipment, tells the crew of the Wheel that the Doctor's name is "John Smith". The Doctor subsequently adopts this alias several times over the course of the series, often prefixing the title "Doctor" to it. This name is particularly prominent during his third incarnation when, as scientific advisor to UNIT, he gives it to Brigadier Lethbridge-Stewart to be put on his official credentials. The Eighth Doctor's companion Grace briefly refers to him by the alias "Dr Bowman" in the 1996 Doctor Who television movie.
In the audio adventure The Sirens of Time when the 5th Doctor is asked his name, he states: "I'm the Doctor." To which, he's answered: "Doctor? That's a profession, not a name." The Doctor is then quoted as saying: "It's all I have."
In "New Earth", it is implied that the Doctor is part of the prophecy of the Face of Boe and is referred to as "The Lonely God". In "Tooth and Claw", having landed in Scotland, the Tenth Doctor introduces himself as "Dr James McCrimmon" from the township of Balamory, referencing the Second Doctor's companion Jamie. Later in that episode, the Doctor is knighted by Queen Victoria as "Sir Doctor of TARDIS."
To his greatest enemies, the Daleks, the Doctor is known as the Ka Faraq Gatri, the "Bringer of Darkness", "Destroyer of Worlds" or "The Oncoming Storm". This is first mentioned in the novelisation of Remembrance of the Daleks by Ben Aaronovitch and subsequently taken up in the spin-off media, particularly the Virgin New Adventures books and the Doctor Who Magazine comic strip. In "The Parting of the Ways", the Doctor claims that the Daleks call him "The Oncoming Storm" — this name is used by the Draconians (whose word for it is "Karshtakavaar") to refer to the Doctor in the Virgin New Adventures novel Love and War by Paul Cornell.
The series has also occasionally toyed with the Doctor's identity (or lack thereof). In the first part of The Mysterious Planet, the Doctor suggests writing a thesis on "Ancient Life on Ravolox, by Doctor...", but is interrupted by Peri. In The Armageddon Factor, the Time Lord Drax addresses the Fourth Doctor as "Thete", short for "Theta Sigma". Later, in The Happiness Patrol, this was clarified as a nickname from the Doctor's University days; he is called by this name again in the Paul Cornell novel Goth Opera. In Remembrance of the Daleks the Seventh Doctor produces a calling card with a series of pseudo-Greek letters inscribed on it (as well as a stylised question mark). This may be a reference to Terrance Dicks' and Malcolm Hulke's book The Making of Doctor Who (1972), which claims that the Doctor's true name is a string of Greek and mathematical symbols.
The question mark motif was common throughout the eighties, in part as a branding attempt. Beginning with season eighteen, the Fourth through Seventh Doctors all sported costumes with a red question mark motif (usually on the shirt collars, except for the Seventh Doctor — it appeared on his pullover and in the shape of his umbrella handle). In the 1978 serial The Invasion of Time, the Fourth Doctor is asked to sign a document; although the signature itself is not directly seen on screen, his hand movements clearly indicate that he signs it with a question mark. A similar scene occurs with the Seventh Doctor in Remembrance of the Daleks.
It was mentioned by Tom Baker, the Fourth Doctor, during an interview with The Age in 2003, that the Doctor is called so because he is "a doctor of time and relative dimension in space". Apart from being called a doctor of the TARDIS, the Doctor has also been referred to as just a "doctor of time travel".
Perhaps complicating the matter is that, from the first television serial through to Logopolis (the last story of Season 18 and also of the Tom Baker era), the lead character was credited as "Doctor Who" (or sometimes "Dr Who"). Starting from Peter Davison's first story, Castrovalva (the first story of the series' Season 19) to the end of Season 26, he is credited simply as "The Doctor".
This format is continued in the 1996 television movie for Paul McGann's credit, while Sylvester McCoy's incarnation is credited as "The Old Doctor". For the 2005 revival starring Christopher Eccleston, the credit reverted to "Doctor Who". However, in "New Earth", and subsequent stories featuring David Tennant, the character is once again identified in the closing credits as "The Doctor", with The Christmas Invasion being the only episode to feature David Tennant in which he is credited as playing "Doctor Who". According to Doctor Who Magazine #367 this reversion was specifically requested by Tennant.
The original concept of regeneration or renewal was that the Doctor's body would rebuild itself in a younger, healthier form. The Second Doctor was intended to be a literally younger version of the First; biological time would turn back, and several hundred years would get taken off the Doctor's age, rejuvenating him. In practice, however, after the Doctor stated his age in the Second Doctor serial The Tomb of the Cybermen (1967), the Doctor's age has been recorded progressively, however many regenerations the Doctor goes through (but see below). Coincidentally or otherwise, the general trend has been toward increasingly younger actors for the role.
The actors who have played the Doctor in the series, and the dates of their first and last regular television appearances in the role, are:
Actors who have played the Doctor in the Dr. Who cinema films:
Actors who have played the Doctor canon status unclear:
Throughout his regenerations, the Doctor's personality has retained a number of consistent traits. Its most notable aspect is an unpredictable, affable, clownish exterior concealing a well of great age, wisdom, seriousness and even darkness. While the Doctor can appear childlike and jocular, when the stakes rise, as, for example, in Pyramids of Mars, he will often become cold, driven and even callous. Another aspect of the Doctor's persona, which, though always present, has been emphasised or downplayed from incarnation to incarnation, is compassion. The Doctor is a fervent pacifist and is dedicated to the preservation of sentient life, human or otherwise, over violence and war, even going so far as to doubt the morality of destroying his worst enemies, the Daleks, when he has the chance to do so in Genesis of the Daleks, and again in "Evolution of the Daleks". He also, in The Time Monster, begs Kronos to spare the Master torment or death, unintentionally winning the evil Time Lord's freedom, which he tells Jo Grant was preferable anyway, and forgives the Master for his actions in "The Sound of Drums" and "Last of the Time Lords", vowing to take responsibility for his former friend.
Nonetheless, the Doctor will kill when given no other option and occasionally in self-defence; examples of this can be seen in The Krotons, Spearhead from Space, The Three Doctors, The Brain of Morbius, The Talons of Weng-Chiang, The Invasion of Time, Earthshock, The Two Doctors, Silver Nemesis, "The Christmas Invasion", "Tooth and Claw", "The Runaway Bride", "Smith and Jones", "Partners in Crime" and most notably in Remembrance of the Daleks when he arranges for the planet Skaro to be destroyed; it is also suggested he may have been responsible for destroying both the Dalek and Time Lord races in order to end the Time War referenced numerous times in the series beginning in 2005. Another example of the Doctor purposely taking a life is The Sontaran Experiment, where he tells Harry Sullivan to remove a device from the Sontaran ship, an act which results in the death of the Sontaran. In the 2005 episode "The End of the World", the Doctor teleports Cassandra back onto the ship and does nothing to prevent her death, even ignoring her cries for help and pity. In situations where fixed points in history must be preserved, the Doctor is sometimes faced with hard choices resulting in the deaths of many; In The Visitation he started the Great Fire of London, and in "The Fires of Pompeii" he caused the volcano above Pompeii to erupt, which killed everyone in the city (but saved the rest of the world). On other occasions he is seen to be critical of others who use deadly force, such as his companions Leela in The Face of Evil and Talons of Weng-Chiang, or Jack Harkness in "Utopia".
The Doctor has a deep sense of right and wrong, and a conviction that it is right to intervene when injustice occurs, which sets him apart from his own people, the Time Lords, and their strict ethic of non-intervention.
Although throughout his regenerations the Doctor remains essentially the same person, each actor has purposely imbued his incarnation of the role with distinct quirks and characteristics and the production teams purposefully dictate new personality traits for each actor to portray.
Another example is in The Tomb of the Cybermen when the Doctor is identified as "English" and, dissembling, plays along. Though David Tennant speaks with a natural Scottish accent, he plays the Doctor with an Estuary accent (apart from when, in the Highlands-set episode "Tooth and Claw", the character is pretending to be a local). According to producer Russell T Davies, this was intended as a consequence of spending so much time with Rose. "The Christmas Invasion" would have alluded to this, but the line was cut.
Davies also said that after Eccleston's accent, he did not want Tennant "touring the regions" with a Scottish one, and so asked Tennant to affect the same accent he used for the earlier BBC period drama Casanova.
When asked if he is English/British, the Doctor has been known to reply: "No, but thank you for the compliment." In the Big Finish audio adventure The Sirens of Time the captain aboard a German U-boat assumes he is English because of the way he pronounces his words. Quote: "So, you speak German, ... but you speak it like an English gentleman."
The Doctor's clothing has been equally distinctive, from the distinguished Edwardian suits of the First Doctor to the Second Doctor's rumpled, Chaplinesque attire to the frills and velvet of the Third Doctor's era. The Fourth Doctor's long frock coat, loose fitting trousers, occasionally worn wide-brimmed hat and trailing, multistriped scarf added to his somewhat shambolic and bohemian image; the Fifth's Edwardian cricketer's outfit suited his youthful, aristocratic air as well as his love of the sport (with a stick of celery on the lapel for an eccentric touch); and the Sixth's multicoloured jacket, with its cat-shaped lapel pins, reflected the excesses of 1980s fashion. The Seventh Doctor's outfit — a straw hat, a coat with two scarves, a tie, checked trousers and brogues/wingtips — was more subdued and suggestive of a showman, reflecting his whimsical approach to life. In later seasons, as his personality grew more mysterious, his jacket, tie, and hatband all grew darker.
Throughout the 1980s, question marks formed a constant motif, usually on the shirt collars or, in the case of the Seventh Doctor, on his sleeveless jumper and the handle to his umbrella. The idea was grounded in branding considerations, as was the movement starting in Tom Baker's final season toward an unchanging costume for each Doctor, rather than the variants on a theme employed over the first seventeen years of the programme. When the Eighth Doctor regenerated, he clad himself in a 19th century frock coat and shirt based around a Wild Bill Hickok costume, reminiscent of the out-of-time quality of earlier Doctors and emphasising the Eighth Doctor's more Romantic persona.
In contrast to the more flamboyant outfits of his predecessors, the Ninth Doctor wore a nondescript, worn black leather jacket, V-neck jumper and dark trousers. Eccleston stated that he felt that such definitive "costumes" were passé and that the character's trademark eccentricities should show through their actions and clever dialogue, not through gimmicky costumes. Despite this, there is a running joke about his character that the only piece of clothing he changes is his jumper, even when trying to "blend into" an historical era. The one exception, a photograph of him taken in 1912, wearing period gentleman's clothing, resembles the style of the Eighth Doctor.
The Tenth Doctor sports either a blue or a brown pinstripe suit - usually worn with ties - a tan ankle-length coat and trainers, the latter recalling the plimsolls worn by his fifth incarnation. Also like that incarnation (and his first one), he occasionally wears spectacles: a pair with brown, thick-rimmed frames. In the 2007 Children in Need special he states that he doesn't actually need the glasses to see, but rather wears them to look clever. On some occasions he wears a black tuxedo with matching black trainers. In interviews, Tennant has referred to his Doctor's attire as geek chic. According to Tennant he had always wanted to wear the trainers, however, the overall costume was influenced by an outfit worn by Jamie Oliver in a TV interview on the talk show Parkinson.
The Tenth Doctor says in "The Runaway Bride" that, like the TARDIS, his pockets are bigger on the inside. The Second, Fourth and Seventh Doctors routinely carried numerous items in their coats without this being conspicuous.
In the original series, with the exception of the change from Troughton to Pertwee, regeneration usually occurred when the previous Doctor was near "death". The changeover from McCoy to McGann was handled differently, with the Doctor actually dying and being dead for quite some time before regeneration occurred. The Eighth Doctor comments at one point in the television movie that the anesthesia interfered with the regenerative process, and that he had been "dead too long", accounting for his initial amnesia.
The 2005 series began with the Ninth Doctor already regenerated and fully stabilized, with no explanation given. In his first appearance in "Rose", the Doctor looked in a mirror and commented on the size of his ears, suggesting that the regeneration may have happened shortly prior to the episode, or that he has not examined himself in the mirror recently. However, the Ninth Doctor's appearances in old photographs, without being accompanied by Rose, may also suggest that he had been regenerated for some time. Russell T Davies, writer/producer of the new series, stated in Doctor Who Magazine that he has no intention of showing the regeneration in the series, and that he believed the story of how the Eighth Doctor became the Ninth is best told in other media. In Doctor Who Confidential Davies revealed his reasoning that, after such a long hiatus, a regeneration in the first episode would not just be confusing for new viewers but also lack dramatic impact, as there would be no emotional investment in the character before he was replaced.
Eccleston stepped down from the role at the end of the 2005 series, and the Ninth Doctor regenerated into the Tenth in "The Parting of the Ways". It remains to be seen whether the Ninth Doctor will appear again, although Russell T Davies has stated that he does not intend to bring back former Doctors. (Despite this, Peter Davison did briefly reprise the role of the Fifth Doctor in the 2007 Children in Need charity special alongside Tenth Doctor David Tennant.)
It was established in The Deadly Assassin (1976) that a Time Lord can regenerate twelve times before permanently dying - a total of thirteen incarnations. In the 1996 television movie the Eighth Doctor explicitly said that a Time Lord has "thirteen lives". (The Doctor's enemy, The Master has, however, been shown circumventing this limit on several occasions.) In "The Christmas Invasion" it was stated the regenerative cycle creates a large amount of energy that suffuses the Time Lord's body. As demonstrated by the Tenth Doctor for the first time in that story, in the first fifteen hours of regeneration this energy is enough to even rapidly regrow a severed hand.
The Doctor's regenerations are usually as a result of his previous incarnation sustaining mortal injury or (in one case) having a change forced on him by the Time Lords. Other Time Lord regenerations, like Romana's, have not been as dramatic or painful.
The Doctor frequently experiences a period of instability and partial amnesia following regeneration. Some post-regeneration experiences have been more difficult than others. In particular, the Fifth Doctor began reverting to his previous personalities and required the healing powers of the TARDIS's "Zero Room" to recuperate (Castrovalva). The Sixth Doctor experienced extreme paranoia and flew into a murderous rage, nearly killing his companion (The Twin Dilemma). The Eighth Doctor experienced amnesia (1996 Doctor Who television movie).
The regeneration from the Ninth to the Tenth Doctor at first seemed smooth, with the Doctor regenerating standing up for the first time ("The Parting of the Ways"). However, shortly thereafter he began to experience spasms and became somewhat manic, frightening his companion as he pushed the TARDIS to dangerous extremes (Children in Need mini-episode). After crash-landing the TARDIS, the Doctor collapsed and remained unconscious for most of the next fifteen hours ("The Christmas Invasion"). The experience was traumatic enough to cause one of his hearts to temporarily stop beating.
As noted above, the newly regenerated Tenth Doctor was able to regrow his hand when it was severed at the wrist during a swordfight with the Sycorax leader. This ability had never been exhibited before.
The TARDIS also appears to aid in the regenerative process. Of the four occasions the Doctor regenerates outside the TARDIS, one was forced on him by the Time Lords (The War Games), one required a Time Lord to give the Doctor's cells a "little push" to start the process (Planet of the Spiders), one needed the TARDIS Zero Room to help him recover (Castrovalva) and the last apparently occurred a few hours after he had actually "died", leaving him with temporary amnesia (the 1996 television movie).
In "Journey's End", the Tenth Doctor manages to avert his own regeneration, using some of the energy to heal himself then channeling the remaining energy into his severed hand, thus retaining his appearance and personality. The question of whether this partial regeneration process uses up one of this thirteen incarnations is left open. Later in the episode, the energy left over from the regeneration forms a "new" Doctor when Donna Noble inadvertently causes a "human biological metacrisis". This Doctor is part Time Lord and part human, possessing the Doctor's memories and physical appearance but also inheriting some of Donna Noble's personality traits. The part-human Doctor also has only one heart, ages like a human, and cannot regenerate. At the same time, the residual energy imbues Donna with the vast intellect of a Time Lord. However, the knowledge is too much for her human mind to handle and at the end of the episode the Doctor has to remove all her memories of her time with him in order to save her life.
In the early serials The Edge of Destruction and The Sensorites, it appeared that the First Doctor had only a single heart. The novel The Man in the Velvet Mask by Daniel O'Mahony suggests that Time Lords only grow their second heart during their first regeneration. In The Mind of Evil, "The Christmas Invasion" and "The Shakespeare Code" one of the Doctor's hearts temporarily stops beating due to intense trauma.
Also during his first regeneration, and for similarly unclear reasons, the Doctor's clothes (save for his cloak and ring, both of which quickly thereafter fall off) changed along with his body (The Power of the Daleks); on all subsequent regenerations the new Doctor generally continues to wear the clothing he regenerated in until he selects a new outfit (though due to a continuity error, the regeneration from the Fourth to the Fifth Doctors included a change of footwear).
In The Brain of Morbius (produced shortly before The Deadly Assassin), visual images displayed during a mental battle between the Fourth Doctor and Morbius can be taken as implying that the Doctor had at least eight incarnations prior to the First Doctor. However, multiple dialogue references throughout the series (particularly in The Three Doctors, Mawdryn Undead and The Five Doctors) contradict this, as well as the fact that the Doctor has regenerated six times since then (as stated in "School Reunion"). Explanations have included theories that the images were of Morbius's previous incarnations (two images that are certainly Morbius also appear, and the game seems to have a symmetrical arrangement), or false images induced by the Doctor. The Doctor Who novels have suggested that these may have been faces of the Other, a figure from Gallifrey's ancient past and the genetic predecessor of the Doctor (although being from the tie-in novels, the canonicity of this character is debatable). The producers, however, intended that these were, in fact, figures from the Doctor's past. Producer Philip Hinchcliffe has said, "We tried to get famous actors for the faces of the Doctor. But because no one would volunteer, we had to use backroom boys. And it is true to say that I attempted to imply that William Hartnell was not the first Doctor. Other indications are given on screen to suggest the same thing, such as the references from the 'Cartmel Masterplan' and the secondary control room, which the Doctor says he used before (The Masque of Mandragora). The alternate console room also contained articles connected to the second (a recorder) and third (a ruffled-front shirt) Doctors, suggesting use of the room during those incarnations.
In the Sixth Doctor story arc The Trial of a Time Lord, a Time Lord with the title of the Valeyard (played by Michael Jayston) was revealed to be a potential future Doctor, a "distillation" created somewhere between his twelfth and final incarnations and embodying all the evil and malevolence of the Doctor's dark side. The Valeyard was defeated in his attempt to actualise himself by stealing the Sixth Doctor's remaining regenerations, however, and so may never actually come to exist.
The idea of an "in-between" version of the Doctor has its precedents. In Planet of the Spiders, a Time Lord's future self (described as a "distillation" of the future incarnation) was shown to exist as a corporeal projection that assisted his then-current incarnation. In Logopolis, an eerie and mysterious white-clad figure known as the Watcher assisted in the transition between the Fourth and Fifth Doctors. Nyssa commented that the Watcher "was the Doctor all the time" as he merged with the supine form of the fourth Doctor, regeneration beginning just before the merging is complete.
Perhaps the most controversial element from the 1996 television movie was the revelation that the Doctor is half-human ("on [his] mother's side"). The spin-off novels and audios have tried various methods to explain this revelation, suggesting that the Doctor retained some human DNA from his time as Dr John Smith (in which the Doctor, using bought technology, became biologically human with a different persona unaware of his Time Lord self) in the Virgin New Adventures novel Human Nature, that his origins have become muddied by agents manipulating his personal timestream (the Eighth Doctor Adventures novel Unnatural History), or that only his mother's incarnation at the time of his birth was Human. In the New Series Adventures novel The Deviant Strain by Justin Richards, the Doctor comments that his DNA is "close" to that of humans. However, as noted above, the canonical nature of the novels is uncertain. The idea of a "half-human" Doctor is further discredited by the 2008 series finale "Journey's End", wherein the Doctor is presented as being fully Gallifreyan.
The Time Lord ability to change species during regeneration is referenced by the Eighth Doctor in relation to the Master in the television movie, being supported by Romana's regeneration scene in the 1979 serial Destiny of the Daleks. The Daleks also implied during the events of The Daleks' Master Plan (1965–66) that the First Doctor's humanoid form is not his actual appearance. The new series has not made any allusions to mixed parentage, simply referring to the Doctor as "alien" or "Time Lord". However, the trade paperback Doctor Who: The Legend Continues by Justin Richards, published to coincide with the new series, refers to the Doctor as half-human. The 2007 Tenth Doctor episodes "Human Nature" and "The Family of Blood", adapted from the above-mentioned Seventh Doctor novel, Human Nature, also show the Doctor using technology to become biologically human, although he does so through Time Lord science. Later, in "Utopia", the Master is revealed to have undergone the same process.
The BBC novel The Eight Doctors was written by respected Doctor Who writer Terrance Dicks, the same author who wrote The Five Doctors. In it, he tries to reconcile the continuity errors of the 1996 movie, while having the Eighth Doctor meet and interact with each of his previous selves.
Physical contact between two versions of the same person can lead to an energy discharge that shorts out the "time differential". This is apparently due to a principle known as the Blinovitch Limitation Effect, and was seen when the past and future versions of Brigadier Lethbridge-Stewart touched hands in Mawdryn Undead. Oddly, the Doctor's incarnations do not appear to suffer this effect when encountering each other and shaking hands. This has never been explained. An essay in the About Time series by Lawrence Miles and Tat Wood suggests that Time Lords are somehow exempt from the effect by their very nature. Rose Tyler is seen holding an infant version of herself in "Father's Day", with no visible energy discharge, but the contact does allow the Reapers to enter the church in which the Doctor and several others are taking refuge. While doing a live commentary on the episode at the 2006 Bristol Comic Expo, episode author Paul Cornell said that this is supposed to be due to the Blinovitch Limitation Effect, even though it is not mentioned by name. He also suggested that the lack of a spark may be down to the fact that the Time Lords were no longer around to manage anomalies.
The interaction of the Doctor's various incarnations produces a continuity anomaly that requires suspension of disbelief on the part of viewers, as one may assume that his past selves would forget that he would later regenerate. In Castrovalva, the newly-regenerated Fifth Doctor clearly indicates that the outcome of his regeneration cannot be predicted; however, the Fifth Doctor should have had memories from his earlier incarnations of having met himself per the events of The Three Doctors and The Five Doctors. Also, the Second, Third and Fifth Doctors should be already familiar with the events of The Five Doctors, having already lived through them multiple times. It has been suggested in fandom that the Time Lords erase the Doctor's memory after such encounters (and in The Two Doctors there is mention of Dastari administering to the Second Doctor a drug that he bemoans "affects the memory"); the novel The Empire of Glass features the First Doctor directly after his return from the events of The Three Doctors, his memory of the adventure having been totally erased barring a vague recollection of meeting "a dandy and a clown". The Virgin Missing Adventures novel Cold Fusion by Lance Parkin suggests that memory-erasure is sometimes, but not always, due to something called "Blinovitch Conservation".
In the 2006 episode "School Reunion", the Tenth Doctor and Sarah Jane Smith both seem to indicate in dialogue that they haven't seen each other since her departure from the TARDIS in The Hand of Fear, although this contradicts their having met later during The Five Doctors. She, in that story, does not realise that the Fifth Doctor is a later incarnation of the third and fourth Doctors with whom she had previously travelled. In "Time Crash", the Tenth Doctor remembers and reproduces what he saw himself do when he was the Fifth Doctor, a fact that seems to surprise the Fifth Doctor himself.
Russell T Davies has expressed a dislike for stories in which multiple incarnations of the Doctor meet, stating that he believes they focus more on the actors than on the story itself. David Tennant had shown enthusiasm for the idea of a multi-Doctor story, opening the possibility of further appearances by Paul McGann and Christopher Eccleston. However, he has expressed doubts about the practicality of shows involving multiple previous Doctors, given that three of the actors who played the character are now deceased.
Since the series revival, there has been one multi-Doctor story, the Children in Need special Time Crash. Before that, the only references to past incarnations (from 1963 to 1996) have been in the aforementioned episode "School Reunion" (in which the Doctor acknowledges having regenerated "half a dozen times" since last seeing Sarah Jane) and in drawings that the Doctor (who has temporarily become human to hide from the Family Of Blood) makes based on dreams of his other life in the 2007 episode "Human Nature". Seen on screen are the First, Fifth, Sixth, Seventh and Eighth Doctors, but a fuller view briefly available on the BBC website depicted all ten incarnations.
Time Crash featured Peter Davison returning as the Fifth Doctor. This event is explained as occurring due to the current Doctor having left his shields down when rebuilding the TARDIS following "Last of the Time Lords" and then accidentally crossing the Fifth Doctor's timeline, allowing the two TARDISes to merge. When the Tenth Doctor effortlessly averts the impending Belgium-sized hole in the Universe caused by this temporal anomaly, he reveals having known what to do because he saw himself do it as the Fifth Doctor and remembered. He goes on to tell the Fifth Doctor how fond he was of his incarnation and how he influences the current Doctor's personality.
For a list of all actors who have played the Doctor see List of actors who have played the Doctor.
The Third Doctor implied in Doctor Who and the Silurians and in The Mind of Evil that he had a lifetime that covered "several thousand years", though in either case he may have been referring to the breadth of time he had visited (or was able to visit) rather than actually lived through, or perhaps his own life expectancy. While the Doctor's age has never been a known quantity, these numbers are the most difficult to reconcile with the rest of the series.
By the time of The Brain of Morbius, the Fourth Doctor was stated to be 749 years old ("something like 750 years" in the prior Pyramids of Mars). In The Ribos Operation, the first Romana said the Doctor was 759 years old and had been piloting the TARDIS for 523 years, making him 236 when he first "borrowed" it. In Revelation of the Daleks the Sixth Doctor was 900 years old, and in Time and the Rani, the Seventh Doctor's age was 953, the same as villainous Time Lady the Rani (in both serials, the Doctor's age is stated in dialogue). In Remembrance of the Daleks the Seventh Doctor said that he had "900 years’ experience" rewiring alien equipment. At the beginning of the 1996 television movie, the Seventh Doctor was shown to have a 900-year diary in his TARDIS.
In the spin-off prose fiction, the Sixth Doctor celebrated his 991st birthday in the short story "Brief Encounter: A Wee Deoch an..?", written by Colin Baker himself, in Doctor Who Magazine Winter Special 1991: UNIT Exposed, the Seventh Doctor celebrated his 1,000th birthday in Set Piece by Kate Orman, and the Eighth Doctor declared his age to be 1,012 in Vampire Science by Orman and Jonathan Blum. The Eighth Doctor also spent nearly a century on Earth during a story arc spread over several novels.
In the 2005 series, the Doctor's age is stated in publicity materials as 900 years, and in "Aliens of London", he says, "Nine hundred years of time and space, and I've never been slapped by someone's mother." Rose follows up by asking him if he is 900 years old, and he replies affirmatively, though it is unclear whether he is being disingenuous. He restates this as "Nine hundred years of phone box travel and it's the only thing left that surprises me", however, in "The Empty Child". In "Voyage of the Damned", the Tenth Doctor states that he is 903 years of age, the first time since Time and the Rani that an exact number has been stated in dialogue; previously, the Master also indicated the Doctor's age to be about 900 in the "The Sound of Drums"/"Last of the Time Lords" story arc.
How this figure is to be reconciled with the Doctor's age in the rest of the series and spin-off media is uncertain.
In the 2006 episode "Rise of the Cybermen", the Doctor transfers part of his life energy to a component of the TARDIS in hopes of regenerating the disabled craft; he states that he has given up 10 years of life in doing so.
At the end of "The Sound of Drums", the Master ages the Doctor by 100 years using his laser screwdriver, leading the Doctor to assume an elderly appearance. In "Last of the Time Lords", the Master states to the population of Earth that the Doctor is nine hundred years old, and informs his subjects he will show them the Doctor's true form, suspending his ability to regenerate. The Master proceeds to age the Doctor further with his laser screwdriver, reducing him to a tiny, wrinkled being subsequently imprisoned inside a bird cage until reverted to his current form with the help of Martha Jones and the entire population of Earth.
During the initial series, William Hartnell's age precluded any involvement of the character with the only other female lead at the time. The First Doctor did flirt with — and was accidentally engaged to — the character Cameca in The Aztecs; although this was part of a ploy to get the TARDIS back, there was a hint of mutual attraction in Hartnell's performance (especially as he is ultimately unable to leave behind the love token she has given him). The fact that the TARDIS crew kept pressing forward in their travels was probably also a factor in preventing any romantic attachments.
As the series progressed and grew more popular among children, the Doctor was firmly established as an avuncular figure to his younger companions, the one exception being the Third Doctor's hurt reaction to his companion Jo Grant's leaving him for an idealistic scientific adventurer whom she describes as "a younger version" of the Doctor (The Green Death). Jo kisses the Doctor on the cheek before she departs, the second time this form of affection had been shown on screen (the second Doctor having similarly kissed Zoe in The War Games).
Despite the press (and, occasionally, the production team) trying to play up the sexiness of some of the female companions or suggesting "hanky panky" in the TARDIS, the series reached the point where any suggestion of the Doctor as a sexual being was avoided altogether. One example was during City of Death, when the Fourth Doctor says to Countess Scarlioni, "You're a beautiful woman, probably," suggesting that he is incapable of appreciating a human woman's attractiveness. This rule held true even when the Doctor's apparent age was closer to those of his companions, or if there was on-screen chemistry between the actors, as there was between Fourth Doctor Tom Baker and his wife-to-be Lalla Ward's Romana II. In fact, a 1980 television commercial broadcast in Australia for Prime Computers showed Baker and Ward romancing each other, in character as The Doctor and Romana, with the commercial ending with The Doctor (prompted by the computer) proposing marriage. These commercials are not, of course, part of the regular series continuity.
In some of the voice overs on Peter Davison's DVDs the matter of physically expressed sexual attention is discussed. According to Peter Davison and Matthew Waterhouse (Adric), John Nathan-Turner had very strict rules laid down about how the companions were allowed to physically interact with the Doctor, and Adric was allowed more physical contact with the Doctor than the female companions because he was male and thus less likely to be romantically attracted.
The perception of the Doctor as essentially an asexual character, uninterested in romance, is why some portions of fandom reacted so strongly to the Eighth Doctor (Paul McGann) kissing Dr. Grace Holloway in the 1996 television movie, breaking the series' long-standing taboo against the Doctor having any romantic involvement with his companions.
The concluding chapter of The Dying Days, an Eighth Doctor novel by Lance Parkin, strongly implies intimacy occurring between the Doctor and Bernice Summerfield. In the Virgin novel Death and Diplomacy, by Dave Stone, the Seventh Doctor implies that he intentionally creates an image of asexuality to keep things simple.
In various novels — especially Lungbarrow — it is also established that Time Lords do not reproduce sexually, but emerge from genetic Looms fully grown, although in equivocal fashion the same book also hints that the Doctor's birth was an exception. This idea was brought to the forefront in the '96 movie, where the Doctor states he is "half-human, on [his] mother's side", suggesting he had a normal human birth, rather than a synthetic Gallifreyan one. Madame de Pompadour's reference to the Doctor's lonely childhood in "The Girl in the Fireplace" would also seem to contradict the Loom theory. The 2007 episode "The Sound of Drums" also directly contradicts this, with Gallifreyan children leaving for the academy when they reach the age of 8. This episode also shows a young Master.
The classic series also made occasional references to the Doctor's childhood on Gallifrey (The Time Monster, State of Decay and Black Orchid), and there had been the occasional reference to Gallifreyan children, also referred to as "Time Tots" by Romana in the audio adventure Zagreus and the incomplete 1979 serial Shada.
In the Big Finish Productions audio play Loups-Garoux, the Fifth Doctor reluctantly agrees to marry the werewolf Ileana De Santos and although he gets out of it later there is, as in Cameca's case, a degree of mutual attraction was present. In the plays involving the Eighth Doctor, his companion Charley confesses her romantic feelings for him in Zagreus, but although he admits he loves her back at the time, it is a highly dramatic moment and the relationship does not progress beyond the platonic.
The recurring novel and audio character Iris Wildthyme, created by Paul Magrs, is first introduced in the Short Trips story Old Flames, is a past romantic interest of the Doctor's who continues to flirt with him whenever they meet. In the audios Iris is played by Katy Manning, the actress who had formerly played Jo Grant during the Third Doctor's era. More of the Doctor's past relationships are explored in The Infinity Doctors and Cold Fusion.
The question of romance is sometimes side-stepped with plot devices in the spin-off media. In the 2001 BBC Books novel Father Time by Lance Parkin, the Doctor adopts an orphaned Gallifreyan-like alien called Miranda. It is implied in the book that Miranda is actually the daughter of the Doctor himself from the far future. Miranda returns in the novel Sometime Never... by Justin Richards, with her own daughter Zezanne. At that novel's end, a time-active being called Soul travels into the past accompanied by Zezanne, the two believing themselves to be the Doctor and Susan, respectively.
In the finale for that season, "The Parting of the Ways", the Doctor even kissed Rose (although the kiss also served a plot purpose). In the same episode, the Doctor's male companion Jack Harkness kisses both the Doctor and Rose in what he believes is a last goodbye. In the New Series Adventures novel Only Human by Gareth Roberts, Rose asks the Doctor how he would know that marrying for love is overrated, to which he cryptically answers, "Who says I don't? You ask the Lady Mary Wortley Montagu." In a December 2005 interview on BBC Four, actor David Tennant, who had just taken the role of the Tenth Doctor, described the relationship between the Doctor and Rose as "basically a love story without the shagging".
In the 2006 series, the Doctor and Rose kiss in "New Earth", but Rose is possessed by Cassandra at the time. In "School Reunion", the arrival of the Doctor's previous companion Sarah Jane Smith and his reaction to seeing her again prompts jealousy and worry from Rose, and Sarah all but admits that she has long been in love with the Doctor. In the same episode, the Doctor hints at deeper feelings for his companions when he remarks to Rose that humans wither and die, and it is hard to watch that "happen to someone who you..." but leaves the rest unsaid. In the following episode, "The Girl in the Fireplace" (written by Steven Moffat), the Doctor shares a passionate kiss and a strong romantic connection with Madame de Pompadour, who takes him away to "dance", but how far the metaphor (coined in the episode "The Doctor Dances") is taken is not seen on screen. Although Rose does not seem to exhibit jealousy towards Madame de Pompadour, she does show some jealousy with regards to a woman called Lucy whom the Doctor speaks kindly of in the next episode, "Rise of the Cybermen". In the novel The Stone Rose, by Jacqueline Rayner, the Doctor kisses Rose after she saves him from being petrified, although it is described as "a kiss of gratitude and joy and unspeakable pleasure at being alive."
In "The Impossible Planet" the Doctor and Rose share an awkward moment when they have to consider settling down in one time period and Rose suggests they do so together, and she later plants a kiss for good luck on the Doctor's spacesuit prior to his descent into the pit. In "The Satan Pit" the Doctor tells Ida Scott that Rose already knows how he feels about her, saying "If you see Rose, tell her...tell her...oh, she knows". In "Doomsday", when the Doctor says his goodbyes to Rose, she finally tells him that she loves him. He begins to reply, but only gets as far as saying her name before he gets cut off, and the next scene shows him standing silently alone, a single tear down his cheek, whatever words he had intended to say remaining unspoken. In the audio commentary for the episode, executive producer Julie Gardner had stated that she thought "he absolutely was going to say it...he was going to tell her he loved her."
In "Smith and Jones", the Doctor says that he would rather 'be alone'. He kisses his new companion, Martha Jones, but only as a "genetic transfer" to distract their pursuers and he is extremely alarmed when she attempts to flirt with him on the TARDIS. The Doctor tells Martha that he and Rose "were together", and is clearly upset over losing her, although Martha points out that it was the Doctor who initiated their kiss and that he chose to take her away in the TARDIS (and moreover, she states that she 'only goes for humans', albeit to hide her disappointment).
Later, in "Daleks in Manhattan", Martha confesses to Tallulah that she is attracted to the Doctor (though Tallulah euphemistically guesses that the Doctor is "into musical theatre", implying that she believes the Doctor is gay). In "Human Nature", as in the original novel, the Doctor's human self, John Smith, falls in love with Joan Redfern (now a nurse, rather than a science teacher) and Martha notes that the Doctor 'had to fall in love with a human' other than herself. When the Doctor is himself again at the end of "The Family of Blood" — during which Martha admits, in an attempt to convince Smith to change back to being the Doctor, that "he is everything to me, and he doesn't even look at me, but I don't care, because I love him to bits, and I hope to God he won't remember me saying this" — he tells Joan he is capable of everything that Smith was, but she rejects his attempt to establish a relationship with her as the Doctor. In the following episode, "Blink", he refers to being "rubbish at weddings, especially my own".
In the penultimate 2007 series episode "The Sound of Drums", when The Doctor then adds a perception filter to the TARDIS keys, allowing the trio to move about unnoticed. When he explains the perception filter to Martha and Jack, Martha is confused at first, but then the Doctor describes it as "...like when you fancy someone, and they don't even know you exist." As Martha stares incredulously at him, Jack looks at her sympathetically and says, "You too, huh?", suggesting that they share a hopeless attraction to the Doctor. Martha unambiguously states in the season finale, "Last of the Time Lords" that she is in love with the Doctor and ultimately chooses to leave him as he seems unable or unwilling to reciprocate.
In the 2008 series various characters assume the Doctor and Donna Noble to be a couple (apart from Agatha Christie in "The Unicorn and the Wasp", who notices that they have no wedding rings), which the pair, having mutually agreed in "Partners In Crime" to strictly be friends, always strongly deny, comprising a running gag. This makes Donna the first companion of the new series - apart from brief companions Adam and Mickey - to not have a romantic interest in the Doctor. In "The Unicorn and the Wasp", the Doctor is kissed by Donna, although it is an act to help him expel poison from his body by shocking him rather than a romantic gesture. In the two-part story "Silence in the Library"/"Forest of the Dead", the character Professor River Song reveals herself to be a future companion of the Doctor, and although the exact nature of her relationship with his future self remains unrevealed, it is intimate enough that she is openly affectionate towards him and is the only known person to be told his true name.
At the conclusion of the 2008 series finale "Journey's End", the Doctor returns Rose Tyler to her parallel universe, asking her to help his part-human, part-Time Lord copy. Rose then asks both Doctors what he was going to say back on Bad Wolf Bay the last time they were there. While the original Time Lord Doctor sadly replies: "Does it need saying?", the part-human Doctor whispers something in her ear, and Rose passionately kisses him. (Speaking about what the part-human Doctor said to Rose, series executive producer Julie Gardner said in Doctor Who Confidential, "Of course he's saying 'I love you.' Of course he is. Even though we don't hear it, of course he's saying 'I love you'.") The Time Lord Doctor then leaves in the TARDIS allowing Rose and the part-human Doctor to have a life and grow old together.
While over the decades several revelations have been made about his background — that he is a Time Lord, that he is from Gallifrey, among others — the writers have often striven to retain some sense of mystery and to preserve the eternal question, "Doctor who?" This back-story was not rigidly planned from the beginning, but developed gradually (and somewhat haphazardly) over the years, the result of the work of many writers and producers.
Understandably, this has led to continuity problems. Characters such as the Meddling Monk, expressly said to be from the same planet as the Doctor, were retroactively labelled Time Lords, early histories of races such as the Daleks were rewritten, and so on. Series writer Paul Cornell, discussing continuity errors, opines that the modern series' "Time War" can explain away (or retcon) such discontinuities, giving the example of Earth's different destructions in The Ark (1966) and "The End of the World" (2005). Writer and future Doctor Who executive producer Steven Moffat has gone further, arguing that "a television series which embraces both the ideas of parallel universes and the concept of changing time can't have a continuity error — it's impossible for Doctor Who to get it wrong, because we can just say 'he changed time'.
Some of the stories during the Seventh Doctor's tenure, part of the so-called "Cartmel Masterplan", were intended to deal with this issue by suggesting that much of what was believed about the Doctor was wrong and that he was a far more powerful and mysterious figure than previously thought. In both an untelevised scene in Remembrance of the Daleks and the subsequent Silver Nemesis it was implied that the Doctor was "more than just another Time Lord." The suspension of the series in 1989 meant that none of these hints were ever resolved. The "Masterplan" was used as a guide for the Virgin New Adventures series of novels featuring the Seventh Doctor, and the revelations about the Doctor's origins were written into the novel Lungbarrow by Marc Platt. However, the canonicity of these novels, like all Doctor Who spin-offs, is unclear.