Ashton Kutcher ran into what he described as a [article id="1656183"]"dirty feet situation"[/article] while shooting the romantic comedy "No Strings Attached." But when we caught up with Kutcher's co-star, Natalie Portman, she told us that particularly sexy scene not only led to filthy feet, but also required a lot of choreography so that she and Kutcher would look "natural" together.

"Some of the things were in [the script]," she explained about the flick, which follows two friends as they try to maintain their sex-with-no-attachment arrangement. "Some of the things were like, 'What are we going to try today?' And also, a lot of it gets choreographed because it's like, 'How are we going to get my hair thing out so that I don't fall on it?' or things like that where I'll be like, 'I can cover you there, and you can [cover me here],' " she added. "So it's very strategic."

We can only imagine how amusing it must have been for Portman and Kutcher to construct those scenes. In addition to the required choreography, Portman admitted to a few makeout mishaps.

"I feel like we probably bumped heads or something," she said of their sex-scene bloopers. "I feel like most of the mistakes were usually like, we would be wearing modesty undergarments or something that would be revealed."

"No Strings Attached" hits theaters on Friday.

Check out everything we've got on "No Strings Attached."

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