Original: She is best known for her roles as Willow Rosenberg on the 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 .
Simplified: She started getting noticed with her roles in Buffy the Vampire Slayer as Willow Rosenberg and in the American Pie movies as Michelle Flaherty .