Alyson Hannigan Interview: On Beauty, Parenthood, and High School

Alyson has natural auburn hair, but she colors it to get her signature red hue. It's all because of her role as Willow Rosenberg in Buffy the Vampire Slayer — and something she had in common with costars Charisma Carpenter and Sarah Michelle Gellar.

"Joss [Whedon] had us all over to his house," Alyson says. "Charisma and Sarah and I all had brown hair at the time. Joss said, 'All of your hair is kind of the same shade. Does anyone want to be red?' I went for it. Eventually Sarah got more and more blond, but it was because we all had a brownish, auburn mane."