Willow Rosenberg is all grown up!

Alyson Hannigan played the witchy Willow on "Buffy the Vampire Slayer" from 1997-2003 -- and her career has been on a roll since.

She was lucky enough to get another incredibly successful TV role, starring on "How I Met Your Mother" ... but some of her costars haven't fared as well.

Click the gallery above to see who got married, had kids and who soared or sizzled professionally -- plus, find out which unlikely cast member won an Emmy and will have a huge role in bringing the final "Hunger Games" movies to the big screen!