Kardashian works her hips with a hula hoop at an Old Navy event in Los Angeles. Plus: Mary-Kate Olsen, Nicole Richie, Rob Pattinson and more

GUEST STAR

Recent MTV Movie Award winner Zac Efron is making the transition to the small screen – temporarily, at least – while shooting a scene for Entourage alongside Jeremy Piven (not pictured) on Tuesday in Beverly Hills.