Rach · CC BY 2.0

Hannigan spent seven seasons playing Willow Rosenberg, the shy teenage witch on Buffy the Vampire Slayer, a role that won her a Saturn Award and became the performance she's still best known for. She was already established from the American Pie films, in which she appeared in every installment from 1999 to 2012, and went on to a decade as Lily Aldrin on How I Met Your Mother. She later hosted the magic-debunking show Penn & Teller: Fool Us.