Willow, played by Alyson Hannigan, is one of the most-loved characters on "Buffy the Vampire Slayer," but she was portrayed by a different actress in the pilot.

Alyson Hannigan has said that becoming a mother changed her — but that's not the only way she's evolved through the years! From hosting competition shows to making millions in real estate, Hannigan is ...

To celebrate, stars Josh Radnor, Alyson Hannigan and Neil Patrick Harris, as well as series co-creator Craig Thomas, spoke with PEOPLE about the "special" episode that started it all "You never know ...