Seth Green's "Buffy" alter-ego was Oz, Willow's guitar-playing/werewolf boyfriend. That role was the start of a successful Hollywood career. Green, now 37, has had a number of memorable roles, including Dr. Evil's son in the "Austin Powers" movies, the dork in "Can't Hardly Wait," the voice of Chris Griffin on "Family Guy" and himself on "Entourage."
He also serves as the co-creator and producer of the TV comedy series "Robot Chicken." Last year, he married actress Clare Grant.
Fun fact: Vampire slaying is genetic. It made sense, then, to introduce Michelle Trachtenberg as Dawn, Buffy's little sister, in season five of the series. Along with her role on "Buffy," Trachtenberg built her career by starring in teen-centric movies like "Ice Princess" and "17 Again."
More recently, she's indulged in the manipulative (sometimes psychotic) Georgina Sparks, the scheming outsider on TV's "Gossip Girl." In real life, the 25-year-old Trachtenberg is a fixture of young Hollywood, and can often be caught party hopping with her co-stars Blake Lively and Leighton Meester.