Alyson Lee Hannigan (born March 24, 1974) is an American actress. She is known for her roles as Willow Rosenberg on the cult classic television series Buffy the Vampire Slayer, Michelle Flaherty in three American Pie films, and Lily Aldrin on the CBS sitcom How I Met Your Mother.
Hannigan was born in Washington, D.C. She is the only child of Emilie Posner, a real estate agent, and Al Hannigan, a truck driver. Hannigan is of Irish descent on her father's side and Jewish on her mother's. Her parents divorced when she was two and she was raised mostly by her mother in Atlanta.
Although Hannigan had appeared in an industrial film for "Active Parenting" as a baby, as well as having starred in a commercial for the Duncan Hines cookie mix in 1978, it was not until 1985, when she moved to Los Angeles, California, that she formally began her acting career. Living with her mother and attending North Hollywood High School, she successfully auditioned for agents while visiting her father in Santa Barbara. After attending North Hollywood High School, she attended California State University, Northridge.