Hannigan was born Alyson Lee Hannigan in Washington, D.C., the daughter of Emilie Posner, a real estate agent, and Al Hannigan, a truck driver. Living with her mother and attending North Hollywood High School, she successfully auditioned for agents while visiting her father in Santa Barbara. In 1997, Hannigan was cast to play Willow Rosenberg, Buffy's best friend, on the television series Buffy the Vampire Slayer. In February 2006, Hannigan starred as Julia Jones in Date Movie, a parody on romantic comedies. She dated and had a very open relationship with the drummer from the band Marilyn Manson, named Ginger Fish, in the 90's.