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Fans hoping to get a glimpse of Chris Evans' bare booty in What's Your Number? will be seriously disappointed.

Though his character drops trou with Anna Faris in the rom-com (in theaters Sept. 30), the 30-year-old actor didn't actually show any skin.

"My butt double is my roommate in Boston! He's a kid I grew up with," Evans told Us Weekly at the film's premiere in Westwood, Calif. Monday.

"Anna said she got a butt double for the bay scene. My buddy Zach was like, 'Who's going to be your butt double?' and I said, 'I don't know. Do you want the gig?'"

According to Evans, it didn't take much for his roommate to impress director Mark Mylod.

"I brought him down, he met the director, did a little spin around and boom -- he's in the movie!" Evans told Us.

The actor added that his roommate was a better choice for the big screen nude scene. "He's got a great ass," Evans laughed.