"Office" star John Krasinski and 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.

Two days after tying the knot in Lake Como, Italy, newlyweds John Krasinki and Emily Blunt landed back at LAX on Monday.



John must have to really get back to his "Office."

Carrie Underwood (left) and Emily Blunt (right) both got married yesterday ... but not to each other.


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