EXCLUSIVE: Zac Efron and Adam DeVine Talk Butt Doubles and Who Has the Softest Lips

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The cast of Mike and Dave Need Wedding Dates sat down with ET, spilling some of the juiciest details from the movie.

In the comedy, opening July 8, Zac Efron and Adam DeVine portray brothers who need to find the perfect dates for their sister's Hawaiian wedding, but instead of the tame girls they were hoping for, the boys find themselves outsmarted and out-partied by an uncontrollable duo played by Anna Kendrick and Aubrey Plaza.

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The cast shows off their raunchy side in the film, and Efron even locks lips with both Kendrick and DeVine, but he kept coy on who had the softest lips.

"All three of you guys have great lips," Efron said. "Let's just leave it at that."

Not satisfied, DeVine pressed for a more solid answer.

"No! Let's get to the bottom of it," DeVine insisted. "I put on so much ChapStick for you, Zac. You have no idea what I went through -- the prep."

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"It was amazing," Efron relented. "It was everything that I dreamed of."

Kendrick may have crushed the dreams of pubescent boys everywhere when she revealed that one scene featuring her backside was actually that of a stand-in.

"It's a butt double," Kendrick confessed.

Efron admitted that the only reason he doesn't use butt doubles is because he hasn't found one that looked better than the real deal.

"They always bring the butt double with the worst butt we've ever seen," Efron said, joking that it might be a clever ploy to get him to show his own derriere. "I think they're manipulating me."