04/06/2011 12:12 pm ET | Updated Jun 06, 2011

'Arthur' Star Jennifer Garner's Russell Brand Crotch Closeup (VIDEO)

Russell Brand is known for the crazy things that come out of his mouth, but Jennifer Garner is well acquainted with his backside, as well.

Garner co-stars with Brand as a woman seeking his billionaire hand in marriage in the new film "Arthur," and told David Letterman about a bit of an intimate moment -- or set of moments -- that the two shared in the film. Garner and Brand feature in a scene in which she's chasing a scantily clad Brand, trying to get him into bed but instead ending up the victim of magnets. And, well, a victim of an up close look at his crotch.

"He was in his underwear, and they were very handsomely made," Garner told the host Tuesday night. "It was Russell and me, right behind him, on all fours. We did it over and over again, so I spent two days just right up against it. So I'm very familiar, in my own way, with the anatomy of Russell Brand -- and it's good."

And how did her husband, Ben Affleck, feel about this scene?

"It's not like I was playing with it!" Garner said, defending her innocence.

Then again, Brand has spoken highly of Garner's kisses -- saying they're like a certain flavor of cake.

Garner will soon take on a decidedly different role; she's starring in an upcoming re-imagining of Agatha Christie's beloved Miss Marple mystery novel series.

"Arthur" hits theaters on Friday; check out the trailer here.