Moviegoers who saw Gabrielle Union in Deliver Us from Eva know she can be a naughty girl. But we see a very different side of the 29-year-old actress in Cradle 2 the Grave (opening today). The Nebraskan beauty not only kicks bad guy butt in the action flick, she also shows off her own, um, assets during a sexy striptease scene.

"I was not really pleased," Union frowns. "It wasn't there when I signed on. I show up for work one day, and [the producers] are like, 'Did you get the new [script] pages?' And I'm like, 'No, hold on. Great... I'm naked.' How did this happen? How [did] I go from 7th Heaven and Bring It On to naked dancing in a strip club?"

Despite the initial shock, the happily married Union was obligated to go on with the show. However, she says she laid down strict ground rules first. "We definitely had to draw some boundaries," she emphasizes. "You are not seeing all the kibbles and bits. You are not getting all of it. I still have to go home to the family reunion this summer, and I'm not doing it with my head bowed and wearing a veil!"

Turns out, shaking her moneymaker wasn't as easy as simply adapting the cheerleading moves she learned for Bring It On. "I was like, 'How am I just supposed to do this lap dance?'" she recalls. "And [the answer was], 'Just go to a strip club and learn.'"

Her eye-rollin' reaction? "I could go to the U.S. Open, but I'm not going to play like Venus and Serena. Do you think I'm just going to get it through osmosis?"

Though she worked with a professional dance trainer, Union couldn't help but be nervous when she finally had to get bootylicious for the cameras. "I was so scared," she says. "It's a wonder what a little choreography and vodka will do for you on days like that."