Alyson Lee Hannigan (born March 24, 1974) is an American actress and television presenter. She is best known for her roles as Willow Rosenberg on the television series Buffy the Vampire Slayer (1997–2003), Lily Aldrin on the sitcom How I Met Your Mother (2005–2014) for which she won a People's Choice Award in 2009, and Michelle Flaherty in the American Pie film series (1999–2012).