Justin Bieber, Sherrie Gahn, Jesse Tyler Ferguson, Ellie Kemper, Mindless Behavior

It's JUSTIN BIEBER'S incredible concert extravaganza for Sherrie Gahn and the kids at Whitney Elementary! JESSE TYLER FERGUSON is the star of one of the funniest comedies on television, "Modern Family," and he was one of Barbara Walters' 10 Most Fascinating People of the Year! This Ellen Show favorite is back to catch up with our host, and he's always as funny as he is fascinating. And the star of one of Ellen's favorite films, ELLIE KEMPER is here! She had Ellen in hysterics in "Bridesmaids" and Ellen's going to find out the scoop on a sequel! She also stars in the hit TV show "The Office," and she's here to tell Ellen all about it. Then, from the man that brought us Lady Gaga, one of the fastest-rising teen sensation pop bands, MINDLESS BEHAVIOR, is here to perform their hit, "Girls Talkin' Bout" from their debut CD, "#1 Girl."