12. Jack McBrayer
McBrayer—best known for his work on 30 Rock—began his improv training in Chicago with iO and the Second City before moving to NYC and starting with UCB.
After years of working in the improv scenes in New York and Chicago, McBrayer landed a recurring gig on Late Night with Conan O'Brien, which put him on the track to national recognition. In addition to McBrayer's work as Kenneth on 30 Rock, he's lent his talents to Ugly Americans, Phineas & Furb, Yo Gabba Gabba!, and Tim and Eric Awesome Show, Great Job!.