First written in the earliest Superman comics, Clark Kent's primary purpose was to fulfill the perceived dramatic requirement that a costumed superhero cannot stay on-duty twenty-four hours a day, or throughout the entirety of a comic book series. As such, Kent acted as little more than a front for Superman's activities. Although his name and history were taken from his early life with his adoptive Earth parents, everything about Kent was staged for the benefit of his alternate identity—he acquired a job as a reporter for the Daily Planet for the convenience of receiving late-breaking news before the general public, providing an excuse for being present at crime scenes and having an occupation where his whereabouts do not have to be strictly accounted for as long as he makes his story deadlines. However, in order to draw attention away from the correlation between Kent and Superman, Clark Kent adopted a largely passive and introverted personality, applying conservative mannerisms, a higher-pitched voice, and a slight slouch. This personality is typically described as "mild-mannered," perhaps most famously by the opening narration of Max Fleischer's Superman animated theatrical shorts. These traits extended into Kent's wardrobe, which typically consists of a softly colored business suit, a red necktie, black-rimmed glasses (which in Pre-Crisis stories had lenses of Kryptonian material wouldn't be damaged when he fired his heat vision through them), combed-back hair and, occasionally, a fedora.
Kent wears his Superman costume underneath his street clothes, which lends itself to easy transference between the two personalities. However, the purpose of this convention outside of fiction is largely dramatic, allowing Kent to rip open his shirt and reveal the familiar "S" insignia when called into action. When in action, Superman usually stores his Clark Kent clothing shrunken down inside a secret pouch hidden inside of his cape, though some stories have shown him leaving his clothes in some covert location (usually places like phone booths) for later retrieval. In addition with the Pre-Crisis comic book title, Superman Family, Kent is featured in a series of stories called "The Private Life of Clark Kent," where he solves problems subtly without changing into Superman.
In the wake of John Byrne's The Man of Steel reboot of Superman continuity, many traditional aspects of Clark Kent were dropped in favor of giving him a more aggressive and extroverted personality (although not as strong as Lois), including such aspects as making Kent a top football player in high school, along with being a successful author and Pulitzer Prize-winning writer. Furthermore, Clark's motivations for his professional writing were deepened as a matter of personal fulfillment in an intellectual field where his abilities give no unfair competition to his colleagues beyond typing extraordinarily fast. Following One Year Later, Clark introduces some techniques to cover for his whereabouts, such as offering to call the police, feigning illness, etc. These, as well as his slouching posture, are references to his earlier mild-mannered Pre-Crisis versions, but he still maintains a sense of authority and his assertive self. Feeling that Clark is the real person and that Clark is not afraid to be himself in his civilian identity, John Byrne has stated in interviews that he took inspiration for this portrayal from the George Reeves version of Superman.
Adopted by Jonathan Kent and his wife Martha Kent of Smallville, USA, Clark (and thus Superman) was raised with the values of a typical small, rural American town including attending the local Methodist Church (though it is debated by comic fans if Superman is a Methodist). Most continuities state that the Kents had been unable to have biological children. In the traditional versions of his origin, after the Kents retrieved Clark from his rocket, they brought him to the Smallville Orphanage, and returned a few days later to formally adopt the orphan, giving him as a first name Martha's maiden name, "Clark." In John Byrne's 1986 origin version The Man of Steel, instead of an orphanage, the Kents passed Clark off as their biologically-born son (after a lengthy months-long series of snowstorms trapped them on their farm).
In the Silver Age comics continuity, Clark gained superpowers upon landing on Earth, and gradually learned to master them, adopting the superhero identity of Superboy at the age of eight. He subsequently developed Clark's timid demeanor as a means of ensuring that no one would suspect any connection between the two alter-egos.
In Metropolis, Superman (as Clark Kent) works as a reporter at the Planet, "a great metropolitan newspaper" which allows him to keep track of ongoing events where he might be of help. Largely working on his own, his identity is easily kept secret. He sees his job as a journalist as an extension of his Superman responsibilities, bringing truth to the forefront and fighting for the little man. Fellow reporter Lois Lane became the object of Clark's/Superman's romantic affection. Lois' affection for Superman and her rejection of Clark's clumsy advances have been a recurring theme in Superman comics, television, and movies.
In the modern age continuity of comics, Clark Kent's favorite movie is To Kill a Mockingbird. According to the DC comics official guide to Superman, Clark enjoys peanut butter and jelly sandwiches, football games, and the smell of Kansas in the springtime. In addition, Clark Kent's favorite baseball team is the Metropolis Monarchs and his favorite football team is the Metropolis Sharks.. As of One Year Later, Clark is in his mid-thirties, stands at 6'5 feet, and is about 225 pounds.
Various reasons over the decades have been offered for why people haven't suspected Superman and Clark Kent of being one and the same. The most common offered is simply that, despite their physical resemblance, Superman and Clark are perceived as too different in mannerisms and personality to be the same individual. In the 1970s, one suggestion was that the lenses of Clark Kent's glasses (made of Kryptonian materials) constantly amplified a low-level super-hypnosis power, thereby creating the illusion of others viewing Clark Kent as a weak and frailer being. However, this reason was abandoned almost as quickly as it was introduced, since it had various flaws (such as stories where Batman would disguise himself as Clark Kent, among others).
Another reason given in the 1987 story "The Secret Revealed" was the public simply does not know that Superman has a secret identity, considering he does not wear a mask, which implies to most that he has nothing to hide. As an added precaution, Superman would vibrate his face (like Jay Garrick, the Golden-Age Flash), slightly so that photographs would only show his features as a blur, thus preventing the danger of photographs of both identities being reliably compared. However, more recent stories showing Superman being photographed have tended to ignore this factor. The 2004 series Superman: Birthright also explained that Superman's eyes are an unnaturally vivid shade of blue. Clark's glasses diffuse the color and make his eyes appear more human in that identity.
Traditionally, Lois Lane (and sometimes others) would often suspect Superman of truly being Clark Kent, though more recent comics often feature the general public assuming that Superman doesn't have a secret identity. In "The Secret Revealed", a super-computer constructed by Lex Luthor calculated Superman's true identity, but Lex dismissed the idea because he could not believe that someone so powerful would want another, weaker identity. In modern comic continuity as of 2006, Lois Lane, feeling anyone like Clark could not be Superman, never suspected the dual identity beyond one isolated incident, before Clark finally revealed it to her. In "Visitor", Lois finds Superman at the Kent farm with Lana Lang and asks him point blank if he is Clark Kent. Before he can answer, the Kents tell her that they raised Superman alongside Clark like a brother.
Some fans have noted that in order for the disguise to be credible, Clark has to be at least as skilled an actor as Christopher Reeve. The films have Clark Kent being massively clumsy, paranoid and of course mild mannered. The actor's portrayal of Clark in the Superman film series was praised for making the disguise's effectiveness credible to audiences. In his book Still Me, Reeve says he based Clark Kent on Cary Grant's nerdy character in Bringing up Baby.
In the commentary track for Superman II: The Richard Donner Cut, Tom Mankiewicz spoke about describing the dual role to Reeve as that he was always playing Superman but when he was Clark, he was playing Superman who was playing Clark Kent.
According to the 2004 limited series Superman: Birthright (which retells Superman's origin), young Clark Kent studies the Meisner technique so that he can seamlessly move between his Clark and Superman personas. As Clark, he drops his head, lowers his shoulders, bends his back forward a little bit and talks in a lighter tone, while as Superman, he stands straight and talks in a deeper tone. In the 2006 feature film, Brandon Routh's performance echoed Reeve's.
Actor George Reeves in the 1950s live-action television series Adventures of Superman brought a naturalistic approach to the dual role, perhaps reasoning that if Clark were too much of a milquetoast, he would not do well in the tough world of investigative journalism, particularly with an aggressive editor like Perry White. Reeves played Clark as moderately assertive, often taking charge in dangerous or risky situations and unafraid to take reasonable risks. This fact was one the main inspirations for the 1980s reboot of the Clark Kent half of the Superman character as described by writer and artist John Byrne in the article Super-Discussions published by Attic Books in Comics Values Monthly Special #2 (1992).
Actor Dean Cain's approach in the 1990s series Lois & Clark: The New Adventures of Superman was to have Clark as a normal, shy, everyday guy demonstrating occasional touches of clumsiness (e.g., pretending to burn his mouth on coffee) but still a highly skilled journalist, much like the current Post-Crisis/Post Infinite-Crisis portrayal. His Superman, by contrast, was very much the model of the classic hero who stood up straight and spoke in a more formal and authoritative voice. In the episode "Tempus Fugitive", the time-traveler Tempus mocks Lois (Teri Hatcher), saying that future historians laugh at her for being "fooled by a pair of glasses", going so far as to insinuate that people in the future consider Lois to be "galactically stupid" for not recognizing Clark to be Superman, however H.G. Wells tells Lois that in truth, the people of the future simply considered Lois to be blinded by love and that it's made her story a compelling one throughout the intervening years.
When crises arise, Clark quickly changes into Superman. Originally during his appearances in Action Comics and later in his own magazine, the Man of Steel would strip to his costume and stand revealed as Superman, often with the transformation having already been completed. But within a short time, Joe Shuster and his ghost artists began depicting Clark Kent ripping open his shirt to reveal the "S" insignia on his chest — an image which became so iconic that other superheroes, during the Golden Age and later periods, would copy the same type of change during transformations (only Spider-Man, through his appearances in comics and Sam Raimi's films, has come remotely close to matching Superman in being connected with the famed shirt-rip shot).
In the Fleischer animated series of theatrical cartoons released by Paramount, the mild-mannered reporter often ducked into a telephone booth or stock room to make the transformation. Since the shorts were produced during the rise of film noir in cinema, the change was usually represented as a stylized sequence: Clark Kent's silhouette is clearly seen behind a closed door's pebble glass window (or a shadow thrown across a wall) as he strips to his Superman costume. Then, the superhero emerges having transformed from his meek disguise to his true self.
In the comic books and in the George Reeves television series, he favors the Daily Planet's store room (the heroic change between identities within the store room is almost always seen in the comics, but never viewed in the Reeves series).
The CBS Saturday morning series The New Adventures of Superman produced by Filmation Studios — as well as The Adventures of Superboy from the same animation house — featured the iconic "shirt rip" to reveal the "S," or Clark Kent removing his unbuttoned white dress shirt in a secluded spot, usually thanks to stock animation which was re-used over dozens of episodes, to reveal his costume underneath while uttering his famed "This is a job for Superman!" line.
In Lois & Clark, Clark's usual method of changing was to either "suddenly" remember something urgent that required his immediate attention or leave the room/area under the pretense of contacting a source, summoning the police, heading to a breaking story's location, etc. Clark also developed a method of rapidly spinning into his costume at super speed which became a trademark change, especially during the third and fourth seasons of the series, and extremely popular with the show's fans.
As a dramatic plot device, Clark often has to quickly improvise in order to find a way to change unnoticed. For example, in Superman (1978), Kent, unable to use a newer, open-kiosk pay phone (and getting a nice laugh from the theater audience), runs down the street and rips his shirt to reveal his costume underneath. He quickly enters a revolving door, spinning through it at incredible speed while changing clothes. Thus made invisible, he appears to have entered the building as Clark Kent and exited seconds later as Superman.
Many fans and Superman scholars believe there to actually be three interpretations. There is firstly who Clark is when he is around trusted friends and family, particularly while on the farm with Martha, or in moments alone with Lois. He is a regular guy, brave, and moral. He then wears two other masks: that of the heroic Superman, and that of the bumbling and goofy Clark Kent who works at the Daily Planet. It should be noted that "bumbling" Clark is an act, but some fans dislike the portrayal of Clark as bumbling and goofy, as they feel it marginalizes his importance to the character. This idea has appeared in comics and various adaptations. In a pre-Crisis story by Alan Moore in DC Comics Presents #85, a sick Kal-El has hallucinations of both the Superman costume and Clark's suit, both offering advice from different viewpoints, and insists that neither of them are real. Rather the reverse relationship exists between Bruce Wayne and Batman, in whose case Bruce Wayne is the fiction and Batman is the reality.
A more academic approach is developed by Jules Feiffer in his series of articles published in The Great Comic Book Heroes that Superman is the real identity of Superman, Feiffer states that most comic book characters were born as their alter egoes (Spider-Man was "Peter Parker" first, Batman was born "Bruce Wayne") Kal-El uses the very blanket he was wrapped in for his trip to Earth as his "costume", which means that Clark Kent is truly the manufactured identity used in order to blend in with humanity, and most important a device to pursue Lois Lane's affections.
Other concepts have become the current accepted canon in most modern versions of the Superman myth (for example, in the DC animated universe Superman cartoon episode "The Late Mr. Kent", wherein Clark Kent is presumed dead, Superman expresses frustration at the idea of not being Clark and having to be someone else instead, because, in his words: "I am Clark Kent. I need to be Clark. I'd go crazy if I'd have to be Superman all the time." In a previous episode, actually the third part of the "Last Son of Krypton" arc, Jonathan 'Pa' Kent assures his adoptive son that he will "always be Clark Kent" and that "Superman just helps out every now and then.")
Clark Kent has also been depicted without the Superman alter ego. In the Elseworlds stories starting with Superman: Last Son of Earth, he is the son of Jonathan Kent, who saves his son from the destruction of the Earth. Clark ends up on Krypton where he is adopted by Jor-El and becomes the planet's Green Lantern.
In a Bill Cosby album, as Kent changes, a cop sees him. (This would have to be after the replacement of wooden-walled phone booths with glass-walled ones.) A policeman orders Kent/Superman out. Clark says, "Look, I told you I'm Superman. Can't you see this red 'S' on my chest?" The cop snaps, "Yeah, and I'm gonna give you a red 'S' and a black 'I' if you don't come out of that phone booth!"
In Superman Returns, Clark has a son with Lois, called Jason White.
This version of Clark Kent was adapted to television in 2001, by Alfred Gough and Miles Millar. Clark Kent has been played continually by Tom Welling, with various other actors portraying Clark as a child. The character has also appeared in various literature based on the Smallville television series, none of which directly continues from or into the television episodes. As of 2007, Smallville's Clark Kent has appeared in eighteen young adult novels. Tom Welling has been nominated for Teen Choice Awards and Saturn Awards for his portrayal of Clark Kent since the show began its first season.
In Smallville, Clark Kent attempts to live the life of a normal human being, and struggles with keeping the secret of his alien heritage from his friends. He has a series long on-again off-again relationship with Lana Lang, the trials of which are based on his lack of honesty about his secret. In contrast to previous incarnations of the character, this Clark Kent starts out best friends with Lex Luthor, whom he meets after saving the latter's life. The pair's friendship eventually deteriorates into hatred for one another. In this series, Clark's powers appear over time. He is not aware of all of his powers at the start of the show; for instance, his heat vision and super breath do not develop until season two and six, respectively, and his power of flight has yet to fully emerge, appearing only in a few rare cases.