Lutz shows off his buff stuff in Studio City, Calif. Plus: Kelly Osbourne, Jon Hamm, Bristol & Mark and more

SURPRISE SERENADE

Look who's partying in the U.S.A.: Tween heavyweights Miley Cyrus and Justin Bieber make sweet music together at the pop sensation's Madison Square Garden concert in New York City on Tuesday. "2nite a dream becomes REAL!!" Bieber Tweeted to fans.