Bump ’N’ Grind! Break dancing! Butt-slapping! Tom Cruise, Katie Holmes and their pals had few inhibitions at the July 22 “Welcome to America” party the couple threw for Victoria and David Beckham in L.A.

As guests like Demi Moore and Ashton Kutcher, Eva Longoria and Brooke Shields mingled, Jim Carrey pretended to spank girlfriend Jenny McCarthy as they boogied—and Will Smith rapped and did splits on the dance floor.

“I can’t believe Will can move like that!” marveled Carrey. But, as Us Weekly reports in its new issue, the real showstopper came when the DJ played “Old Time Rock & Roll,” prompting Cruise to re-enact his famous scene from Risky Business. At one point, he got on his back and kicked his legs in the air, just like in the movie!

In real life, however, the star kept his pants on.