"Office" star John Krasinskiand full-frontal nudist Jason Segel HILARIOUSLY crashed a random girl's bachelorette party last weekend -- and we got the sex doll-filled karaoke footage!!!
It all went down at a bar in Ann Arbor, Michigan -- we're told John and Jason were hanging out with Emily Blunt and "Community" actress Alison Brie ... when the girls at a nearby bachelorette party asked the guys to sing for them.
John and Jason happily obliged -- with a pretty awesome rendition of "Brown Eyed Girl" -- and we're told, the bride-to-be couldn't have been happier.
If you've ever wanted to see Hollywood's hottest women hump a workout ball, then Jimmy Kimmel's post-Oscar sketch mocking exercise infomercials is the video for you!
Make sure you watch the whole thing to catch Lindsay Lohan's cameo mocking her latest legal troubles.
Britney Spears might miss a lot more 'X Factor' auditions ... because she can! Simon Cowell gave Brit damn near free reign in order to sign the pop star to that $15 million deal -- but is it backfiring? We'll tell you what peeps on the set are saying.Plus, Chris Jericho's…