Daniel "Oz" Osbourne (born 1980 in Sunnydale, California) is a fictional character created by Joss Whedon for the cult television series Buffy the Vampire Slayer and Angel. The character is portrayed by Seth Green.
Oz's most outstanding trait is his detached, ironic approach to life, masking a deeply philosophical interior. He is also the lead guitarist for the band Dingoes Ate My Baby, which performs frequently at The Bronze. A high school senior, one year above Willow and the rest of the group, he "tests well", but his only real ambition lies in his music.
He notices Willow in spite of — or perhaps because of — her Eskimo costume at a dance at The Bronze, and seems to be interested in her at first sight. It would take several episodes for the two to actually meet in person. They go into, according to Willow, "some sort of holding pattern, except without the holding or... anything else", even though they had several dates, on one of which he witnesses a vampire being dusted by Buffy for the first time, and thus becoming a member of the Scooby Gang. He is not shocked to learn that vampires exist and merely remarks that it explains a lot. He and Willow eventually share their first kiss and become a couple at the end of the season two episode "Phases".
The episode "Phases" was also the episode where he finds that he has become a werewolf, turning into a monster on the three nights around a full moon, having been bitten on his finger by his pre-adolescent cousin Jordy (interestingly, when Oz calls Jordy's mother, his Aunt Maureen, to ask if Jordy is a werewolf, Maureen is apparently unfazed by the question and readily confirms Jordy's condition, indicating that Oz is not the only exceptionally laid-back member of his family). On his third night as a wolf, Oz is nearly killed by werewolf hunter Gib Cain for his pelt, but saved by Buffy and the Scooby Gang, with whose help he quickly finds a way to minimize the danger posed by the wolf: he locks himself into a cage for the appropriate nights, watched over by the Scoobies in shifts.
Even though he is intelligent (so much so that he, along with Willow, was tracked for a time by "the world's leading software concern") he does not manage to graduate that year, due to several incompletes and failing to attend summer school. He repeats his senior year, now being in the same year as the rest of the gang, and graduates simultaneously with them. During this year, his relationship with Willow goes through rough water as he and Cordelia catch Xander and Willow kissing. They break up, but get back together again after Oz confesses he misses her ("Amends"). In the episode "Graduation Day, Part One", Oz and Willow have sex before the impending confrontation with the evil Mayor Wilkins, concerned that they might die in battle. Willow loses her virginity as a result, but Oz was already not a virgin.
After graduation, he attends UC Sunnydale, together with Buffy and Willow, and is seen taking 'Introduction to Psychology' by Professor Walsh along with them. Unlike the other two, he does not have a dorm room, but stays in a house off campus along with the rest of the band. Because the cage he used to lock himself up on the nights around the full moon was destroyed (along with the rest of the library and Sunnydale High) during the fight against the mayor, he now locks himself up into a cage in a crypt at a local cemetery.
While appearing to the outside world as to have come to terms with his lycanthropy rather easily, evidence arises that he indeed does hold great fear of his werewolf side ("Fear, Itself"), and especially hurting others with it. Moreover, gradually, he starts to see that he and the wolf aren't as separate as he'd like to believe — although in love with Willow, he is irresistibly drawn to another werewolf, Veruca, a fellow UC Sunnydale student, who, unlike Oz, considers the wolf to be her true self. After spending a night in the cage with Veruca, and killing her at the following sunset to protect Willow, Oz resolves to leave Sunnydale so as not to endanger his friends further.
Some months later, Oz returns to Sunnydale, believing that his lycanthropy is now under control through techniques learned in Tibet. Although the moon no longer affects him, he can still transform into the werewolf when faced with strong emotion ("negative stimulation"), such as anger or pain, as he discovers when he finds that Tara Maclay has replaced him in Willow's affections, and when The Initiative seizes him for its experiments. This transformation can occur during the day.
After that discovery, Oz leaves Sunnydale for good (reflecting Seth Green's decision to move on and pursue his film career) soon after the Scoobies, assisted by Riley, break him out of the Initiative complex. He and Willow leave on friendly terms, she even admits that she expects to run into him again at some point in her life. Oz is last seen in Willow's dream in the episode "Restless", as she meets him in college. Oz is not seen again for the remainder of the series' run. His current whereabouts are unknown.
It has been confirmed by Joss Whedon that Oz will reappear in the canonical Buffy the Vampire Slayer Season Eight comics. The arc will be written by Jane Espenson and will star Oz as the main character.
Oz originated as a temporary cast member for the show. He was based on a student with whom Buffy-creator Joss Whedon attended college, as Whedon mentions in his commentary on "Innocence" in the Season Two DVD boxed set. In the writers' original plans Oz was to be killed early in Season Two by a vampire, presumably Angelus, before this dubious honor went to Jenny Calendar. The plan changed, as shown in "Phases" when Oz's plot is expanded as he becomes a werewolf.
In several episodes during Season Four, Oz can be seen wearing a sheepskin jacket, alluding to the Aesopian fable, origin of the well-known phrase "a wolf in sheep's clothing".
Oz also has a highly enhanced sense of smell when in human form. During the episode "Lovers Walk", he is able to smell Willow from great distance although she "doesn't even wear perfume." Oz can also tell that she is fearful by her scent, mimicking the ability apocryphally attributed to many animals, especially canines.
He also demonstrates that werewolves can exert influence on their actions in bestial form. When Oz transforms for his battle with Veruca, he instantly attacks her until she's dead, completely ignoring Willow until killing Veruca.
Oz is also a skilled musician, specializing in electric guitar.
Oz also appears in Buffy expanded universe. He appears in a few comics/novels, most notably the trade paperback Oz (Buffy comic) and the novel Oz: Into the Wild (Buffy novel), which follow his quest to control his wolf-side after his departure in "Wild at Heart".
He also appears in the novel "Queen of the Slayers". In this novel the forces of evil amass to kill Buffy for destroying the Hellmouth in Sunnydale and during a quest she encounters Oz who's the apparent leader of a pack of werewolves that protect the Golden One. Oz and the other werewolves can now completely control their wolf forms and they take part in the final battle of the book during a full moon.