Alyson Hannigan 1989, her first regular role on a TV series came when she was cast in the short-lived ABC sitcom "Free Spirit". As a teenager, Hannigan babysat for the children of her future "How I Met Your Mother" costar, Bob Saget. In 1997, Hannigan was cast to play Willow Rosenberg, Buffy Summers' best friend, on the television series "Buffy the Vampire Slayer". The show became a success, and Hannigan gained recognition, subsequently appearing in several films aimed at teenaged audiences, including "American Pie" (1999), "Boys and Girls" (2000), "American Pie 2" (2001), and "American Wedding" (2003). She also had a guest
Oz (Buffy the Vampire Slayer) Oz (Buffy the Vampire Slayer) Daniel "Oz" Osbourne is a fictional character created by Joss Whedon for the television series "Buffy the Vampire Slayer". The character is portrayed by Seth Green. Green also portrays the character in one episode of the spin-off series "Angel". In "Buffy", Oz is portrayed as a taciturn, guitar-playing teen who becomes boyfriend to Willow (Alyson Hannigan), one of the show's main characters. After first appearing in the episode "Inca Mummy Girl", Oz discovers he is a werewolf in the episode "Phases" and becomes a recurring character throughout the second season. Green is elevated to main