Alyson Lee Hannigan (born March 24, 1974) is an American actress and television presenter. She is best known for her roles as Willow Rosenberg in the television series Buffy the Vampire Slayer (1997–2003), as Lily Aldrin in the sitcom How I Met Your Mother (2005–2014) for which she won a People's Choice Award in 2009, and as Michelle Flaherty in the American Pie film series (1999–2012). Since 2016, Hannigan has hosted the television show Penn & Teller: Fool Us. She also provides the voice of Cla...