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
Buffy the Vampire Slayer was going to play the rest of the scene, and the role, for that matter, and defined the character. Her approach subsequently got her the role. The "Buffy" opening sequence provides credits at the beginning of each episode, with the accompanying music performed by Californian rock band Nerf Herder. In the DVD commentary for the first "Buffy" episode, Whedon said his decision to go with Nerf Herder's theme was influenced by Hannigan, who had urged him to listen to the band's music. Janet Halfyard, in her essay "Music, Gender, and Identity in "Buffy the Vampire Slayer" and "Angel"," describes the