Neil Patrick Harris dished behind-the-scenes details about his horrific “Gone Girl” sex scene with actress Rosamund Pike.

Harris spoke to Conan O’Brien on his TBS talk show about the scene. The actor had two major concerns during the two-day shoot: making sure Pike was comfortable and being aware of the camera angles.

The actor explained he wasn’t concerned with showing off his butt, but letting the crew see his penis was another issue.

“I needed to make sure no one really saw my wang,” he told Conan. “You don't mind a little hint of the wang but you don't want a long, long moment with the wang. So you're conscious of that. You're like, fine if you see my butt and stuff like that, but don't get the camera too low.”

Harris then talked about another nude scene he had to do while performing on stage for play “The Paris Letter.” He described having to do “windmills” and “helicopters” to prepare for the scene.

“It was with Josh Radnor who was on 'How I Met Your Mother' - played Ted,” he said. “It was a flashback scene in the 70s where I had seduced him and we had just had sex and the scene starts with him coming on naked, nervous, and ‘What have I done?’ Then I kind of saunter on as well naked.”

Harris wasn’t the only actor who had a naked scene in the film. “Gone Girl” star Ben Affleck showed off his butt and penis during the David Fincher movie, and his wife Jennifer Garner talked about it during an interview with "The Ellen DeGeneres Show.”

"What I have to say is, 'You're welcome,'" she said, laughing with Ellen. "I just try to consider myself a charitable person and I wanted to give back. You give me so much, I wanted to give something back to all of you."