Even more than his various TV and movie roles, Ashton Kutcher is probably best known as one of Hollywood’s biggest pranksters. With his shows Punk’d and Pop Fiction, the hunky star has essentially made a one-person industry out of tricking his fellow celebs and the media. But surprisingly, Ashton says he draws the line at all this tomfoolery when he’s actually working on a film.

"If you punk your co-stars, people won’t wanna work with you anymore," he explained on Monday’s Today Show, where he and co-star Cameron Diaz appeared to promote their new film, What Happens in Vegas.

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Cameron agreed that this was a wise decision on Ashton’s part. "The biggest thing… is trust," she said about working together on a film, adding that such trust flies right out the window, "if you think that around every corner, you’re going to get slapped in the face!"

This morning also saw the first time that Cameron spoke to the press about the recent loss of her father. "You can’t really sum it up in words," a choked-up Cam told Meredith Vieira when asked to describe what her dad had meant to her. "We’re just so fortunate to have the family that we have."

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