Credit: Jeff Kravitz/FilmMagic

An in-the-buff Ashton Kutcher may seem like no laughing matter, but that's just the reaction the actor is hoping for.

Kutcher explained to E! Online that his sex scenes with Natalie Portman in their upcoming rom-com, No Strings Attached, "are meant to be funny."

Continued the star, "The real challenge was, sort of, you've got 50 people looking at you, you don't have any clothes on, you're with somebody that you don't really know and you're trying to make sure they're comfortable, you're trying to be comfortable and now you've got to be funny."

Luckily he has no problem finding the humor in the bedroom.

"Inherently, I kind of find that sex and intimacy, when it's great, it is funny anyway," Kutcher, 32, said. "Like, you're with someone, you're having fun with someone."

But when it comes to his five-year marriage to Demi Moore, 48, he makes sure to focus on more than the laughs.

"For me, constantly reminding myself, like no matter how amazing my relationship is -- keep working on it, keep finding another level," he said of his romance philosophy. "That's what's really important. Because we all get comfortable and when we get comfortable, we get lazy and when we get lazy, we forget to do the little things."