Channing's Shocking Prosthetic 'Vow' Prank

Cinema w/ Sharlette - 'The Vow'

Channing Tatum and Rachel McAdams must rediscover love after an accident causes Rachel's character to lose her memory in The Vow, and Channing tells ET that he decided to pull a practical joke on her during a nude scene!

"I did have a stunt pee pee that I had made for her for her reaction," says Channing of the scene in which Rachel is surprised by her naked co-star walking into their bedroom. "It was a little prank that I pulled on her. It's in the movie – her reaction was spot on. I didn't have a lot of faith in her reaction because it was cold that day, and I didn't want her to be laughing and pointing. I wanted her to be shocked."

Channing Tatum Goes 'Haywire'

"A prosthetic, yes, that's all true," says Rachel with a laugh, recounting how Channing went to the prop department ahead of time to fabricate "a piece to terrify Rachel with." She adds, "But it was great because I didn't have to pretend … it was funny and got a genuine reaction out of me."

Channing adds, "I'm not shy about being naked, obviously, as you can see in most of my movies."

Rachel McAdams on Her 'Chaotic' Role

In theaters February 10 -- just in time for Valentine's Day -- The Vow stars Channing and Rachel as Leo and Paige, newlyweds whose happiness is derailed by a car accident that erases Paige's entire memory of her relationship with her husband. Refusing to give up, Leo decides to court Paige as if they've just met, with the hope that since they fell in love once, they can do it again. Scott Speedman also stars as Paige's first fiancé, and the cast is rounded out by Sam Neill and Jessica Lange. The film is inspired by a true story.