The polka-dot-wearing actress makes a cheerful arrival to the Late Show with David Letterman. Plus: Blake Lively, Gavin & Gwen, Nick Jonas and more

DRESS REHEARSAL

Rocco DiSpirito and Karina Smirnoff get ready to rumba on the L.A. set of Dancing with the Stars before Monday's episode. Unfortunately, despite the warm-up, the team only earned 16 out of 30 points from the judges.