Kids and celebs shut down Hollywood Boulevard on Sunday for the morning premiere of DreamWorks Animation’s “Kung Fu Panda 2.” A block-long carnival celebrating the pic included video-game tents, photo booths, breakfast buffets and giant panda mascots that posed for cellphone snapshots. They were a light-hearted contrast to the A-lister red carpet running alongside the carnival. “Panda” stars at the Chinese included Angelina Jolie (with Brad Pitt), Lucy Liu, Dustin Hoffman, Seth Rogen and Jack Black, strolling past screaming fans and photogs. In a slight change of scene, thesp James Hong signed autographs, posed and readjusted his hat — a bowl of noodles with a pair of chopsticks.