Seth was born to Herbert, a mathematics teacher, and Barbara, an artist in Philadelphia, PA. The couple already had a daughter, Kaela also an actress. Seth and Kaela were raised in Overbrook Park, PA. It is said that a photograph of him being born was used in an ad campaign for natural childbirth, but Seth's mother has denied this rumor. Seth attended public school and played soccer. He decided to make acting his career at age six when he took part in a workshop in his hometown and after appearing in a summer camp performance of "Hello, Dolly!" Seth actually got his start in commercials as a child including a John Denver Album, Fruit Loops, Carl's Jr., Rally's (the origination of the catchphrase "Cha-Ching!" which still follows Seth around to this day), Wendy's, Jello Pudding Pops, Kodak, Hewlett Packard Printer, California Department of Health Services on Smoking and most recently the US Sci-Fi Channel. One of his commercials was with Sarah Michelle Gellar, when she was four years old.
He went on to appear in such illustrious telly as The X-Files, The Wonder Years, Beverly Hills 90210, Evening Shade, seaQuest DSV (as Wolfman, maybe a sign of things to come?) before his extended exposure on Buffy, the Vampire Slayer as Oz.
He has appeared in many movies including: Hotel New Hampshire, Radio Days (as a young Woody Allen), My Stepmother Is An Alien (as Alyson Hannigan's boyfriend, another omen?), Pump Up The Volume (with Juliet Landau also of Buffy fame), the 1992 movie version of Buffy the Vampire Slayer (his scenes were cut), Austin Powers: International Man Of Mystery, Stonebrook, Idle Hands, Enemy Of The State, Austin Powers: The Spy Who Shagged Me, Can't Hardly Wait.
Interestingly, Seth had a part in the movie version of Buffy - unfortunately, his part ended up on the cutting room floor, though a still photo of him (as a vampire) is on the back of the box of the US video release.
He graduated from Lamberton High School in 1991.
Though Seth has a very large list of credits, he didn't gain notoriety until Buffy the Vampire Slayer and Austin Powers came along.
Now he has less anonymity and a lot of fans to attest to it, from two distinctly separate groups eleven to seventeen-year-old girls and drug-dealers.
While his involvement with the Buffy the Vampire Slayer movie only goes back as far as the cutting room floor of 1992 he is apparently on the cover of the US video release.
In 1997 his return to the realm of Buffy came, it was not as grand as it would become: his contract was only for three episodes in Season Two (namely 'Inca Mummy Girl', 'Halloween' and 'What's My Line, Part One') as Oz, the first person to show an interest in Willow [Alyson Hannigan], but fairly early on it became apparent to Buffy creator Joss Whedon that Seth and Alyson got on well enough to make more of Oz and so he increased Oz's relevance to the story of 'What's My Line' and put him in Part Two (taking a bullet for Willow). Whedon wanted to give the characters besides Buffy [Sarah Michelle Gellar] more of a private life and Willow's love life had really only been explored with Xander [Nicholas Brendon]. Whedon wanted the audience to hate Oz for driving Willow and Xander apart and then love him. He wrote Oz into the big two part story of season two: 'Surprise' and 'Innocence' and gave him a scene with Willow where he tells her how he feels about her and it worked, Oz fans appeared all over. Oz was officially admitted into the Scooby Gang when he saw Buffy slay a vampire at The Bronze, helped steal a rocket launcher from the army and pick up immolated parts of a dead invincible demon. Not bad for a day's work.
Joss Whedon gave a copy of the next episode's script to Seth as a way to convince him to become a regular for the next season. It worked and Oz became the werewolf in 'Phases'. In 'Bewitched, Bothered And Bewildered' he searched for Buffy after Amy [Elizabeth Anne Allen] turned her into a rat. In 'Passion' someone had to die and it was going to be Oz, but his signing up for the third season fortunately scuppered that and the unlucky honour fell to Jenny Calendar [Robia La Morte]. After his rodent recovery duties in 'Bewitched, Bothered And Bewildered' he next appeared in the both parts of the two part Season Two finale 'Becoming, Part Two'. In the latter part of that Willow is in a coma and Xander, sitting at her bedside tells her he loves her, she wakes up and the first thing she says is "Oz?".
He made Entertainment Weekly's '1998 It List,' the magazine's annual pick of the hottest stars.
Oz naturally returned in Season Three in 'Anne' with a promotion to series regular and as part of the Buffy-absent slaying. In 'Dead Man's Party' and 'Faith, Hope & Trick' he is an integral part of the Scooby Gang. The next episode 'Beauty And The Beasts' starts as an Oz feature episode, but becomes a reminder of who Angel [David Boreanaz] is. For the remainder of the season Oz fulfils two roles: Willow's boyfriend and 'boy-in-a-band'. This is primarily due to the sheer amount of screen time devoted to new slayer Faith [Eliza Dushku]. That said he is still great in every scene in which he appears, highlights include 'Band Candy', 'Lover's Walk', 'The Wish', 'Amends', 'The Zeppo', 'Dopplegangland', 'Choices' and 'Earshot'. He becomes increasing under-utilized as the season progresses until 'Graduation Day, Part One and Two' where he has some of his best scenes all year.
Having decided to leave Buffy for a further career in movies Seth handed in his noticed and agreed to appear in the beginning of Season Four. In 'The Freshman' the gang (minus Angel and Cordelia [Charisma Carpenter], who have left for LA and their' own show: Angel) relocate to UC Sunnydale. In 'Living Conditions' Oz spots Veruca [Paige Moss] on campus and is strangely attracted to her (all in a split second). 'The Harsh Light of Day' and it's Angel crossover 'In The Dark' gave Oz double duties as he took the Gem of Amarra retrieved from Spike [James Marsters] and gave it to Angel and then helped Cordelia & Doyle [Glenn Quinn] save the day. In 'Fear, Itself' the gang get to feel the worst fears coming true two of which: Oz losing control of the wolf within and Willow losing Oz would come true two episodes later. Oz is almost infatuated with Veruca all through 'Beer Bad' and discovers that she is a werewolf like him in 'Wild At Heart' and they attack Prof. Walsh [Lindsay Crouse]have sex in wolf form. Realising he has no control over his wolf side he flees Sunnydale and Willow.
When he left to make the thriller 'Knockaround Guys' (with John Malkovich and Barry Pepper) it was not known if he was going to return. It was expected that he would and in a regular role, those with expectations were half right: he did return in 'New Moon Rising' but only as a guest star. Oz claims to have found a cure for his condition and doesn't change on the night of a full moon and he and Willow seem likely to be back together until Willow tells Buffy that she and Tara [Amber Benson] are involved. Oz meets Tara and is enraged and transforms into wolf form warning her to "Run". He is caught by The Initiative and almost killed by Riley [Marc Blucas] because he mistakenly thought Oz was the demon that attacked co - soldier Graham [Bailey Chase]. When Riley realises that it is Oz he attempts to help him escape risking a court martial at the hands of Col. McNamara [Conor O'Farrell] and held in the brig. Willow, Buffy, Xander and Spike attempt to break both of them out with the help of Giles, Anya [Emma Caulfield] and albeit unwittingly Adam [George Hertzberg]. Oz suspects that it is Willow that brings out the wolf in him and leaves again, Willow professes her love to Tara.
He also appears in the season finale, 'Restless' in Willow's dream as a metaphor for her life with him being different to her life with Tara. Only time will tell whether he will return to Buffy or in fact Angel. The rumours say yes, but then they always do. Don't they?
As for the future, Seth is apparently not interested in directing, but he would like to produce, as well as keep acting. He and his best friends Breckin Meyer and Ryan Phillippe have an office where they peruse scripts, and they are aiming to produce films together.
Next on the horizon the dark comedy Scorned. The film, which is based on an idea from Seth and his childhood-friend-turned-screenwriter Hugh Sterbakov, centres on a young engaged couple whose romance takes an ugly turn when they head to college; the affair becomes a grudge match, and the pair's dorm turns into a war zone.