Kellan Lutz Nervous About What “Mother Thinks” of Underwear Ads

 Courtesy of Calvin Klein

Kellan Lutz tells he was completely at ease stripping down to his skivvies to pose for Calvin Klein ads.

"You know I've done other fittings where you have to wear underwear and you're kind of uncomfortable because they look funny or it doesn't fit well. That's the difference with Calvin Klein. They fit great, they're snug and they hold everything in and you look good," the New Moon star, 24, told Us at the Calvin Klein fashion show in New York City Sunday.

Check out more photos of stars showing off their under garments

"In the beginning, I was just, like, 'So, is the temperature going to be hot? Do I need, you know, fluffers maybe?'" he quipped. "They made it really easy. The clothes fit great — there wasn't anything that was riding up, so you don't feel uncomfortable posing."

After the ads were released, though, Lutz joked that he has a few second thoughts.

"But now my nude a*s is going to be all over billboards, we'll see what my mother thinks," he laughed to Us.

See Twilight stars before they were famous!

Lutz appears nearly nude alongside True Blood star Mehcad Brooks, Spanish tennis star Fernando Verdasco and Japanese athlete Hidetoshi Nakata in the ads, which will be officially released — in 3D! — on March 1.

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