Tom Cruise is letting loose!

The actor, 50, partied with his All You Need Is Kill costars Emily Blunt, 29, and Bill Paxton, 57, at Matt Damon's 42nd birthday blowout at London burlesque club The Box in London October 6, sources tell the new issue of Us Weekly (out now).

"They were all having fun," says an onlooker. "Matt and his wife [Luciana] were jumping on couches, kissing and doing shots."

A solo Cruise -- who split with wife Katie Holmes, 33, in late June -- stayed out until 3 a.m., enjoying the club's wild circus and comedy acts. Says the source, "He even got paddled by the transgender hostess!"

For more details on Damon's wild birthday bash, watch this week's Hot Stuff video, as explained by Us Weekly Senior Editor Ian Drew.

Also in the roundup: Gwyneth Paltrow celebrates her 40th birthday with A-list pals Beyonce Knowles, Chelsea Handler and Jake Gyllenhaal; Demi Moore is "not psyched" about ex Ashton Kutcher dating Mila Kunis; and much more!