Megan Fox has been called the hottest girl in the world, but she doesn't take her sex symbol status -- or herself -- too seriously. She couldn't even keep a straight face when she had to take her clothes off for a scene in Judd Apatow's latest movie This Is 40. In a newly released blooper reel for the film, the sultry actress is shown cracking up as co-star Leslie Mann jiggles her cleavage.

In the clip, Fox strips down to a pink bra and underwear as Mann's character marvels at the 26-year-old's fit figure. "Wow, I would put floodlights on them," Mann says as she fondles her co-star's perky breasts. At that, Fox breaks down in giggles and turns away from the camera.

Mann, 40, recently admitted that she had a difficult time with the scene, too -- but for a different reason. "I feel very protective of younger actresses because it was so hard for me in the business," the actress told Yahoo! Movies in a recent interview. "I wanted to get it over [with] as quickly as possible, because I knew it was uncomfortable for her, probably -- or maybe not."

"But just in that situation I knew there were a lot of dirty boys around having weird, gross fantasies," she explained. "And so I wanted to get her shirt back on as quickly as possible."

That said, Mann had no complaints about her part in the scene. "Megan just has great boobs," she gushed to Yahoo! Movies. "Better boobs than I've ever seen in my life."

Unfortunately for Fox's fans, the actress won't be flaunting them so openly in the future, thanks to her son Noah, 4 months, whom she and husband Brian Austin Green welcomed in late September. "It changes your perspective about being overly sexual in a film when you have a baby," the first-time mom told the U.K.'s Daily Mirror in December. "I'm going to be more cautious about choosing films because I'm already thinking about when he's in school, and his friends are going to be showing him my photo shoots with me in a bikini, and he's going to be horrified. So, that will deter me from making some of the choices I made."

This article originally appeared on Usmagazine.com: Megan Fox Giggles as Leslie Mann Gropes Her Breasts in This Is 40 Blooper Reel