Yikes! That didn’t look so fun! Lol.  Michael Phelps broke something that wasn’t a world record — HIS ASS — taking a nasty spill while crowd surfing in a Vegas nightclub this week.

GameTimeGirl


Phelps — who’s STILL in party mode after the London Games — hit up XS nightclub Monday night, and for some reason thought it would be a good idea to crowd surf inside an inflatable raft.

It was not … because the 18-time gold medalist barely made it a few feet before toppling backwards onto his ass.

Thankfully, we’re told he was okay — but the video’s still awesome. Check it out.

TMZ