Zac Efron Talks His 'Neighbors' Shirtless Scenes: 'F--k, This Is My Nightmare'

Efron and co-star Seth Rogen debate who loses their top more in upcoming movie.

Seth Rogen knows how you sell a movie. For example, in the upcoming comedy flick "Neighbors," all you have to do is get co-star Zac Efron naked. Or at least, shirtless.

"I try to make sure there's paparazzi around, because I know it's good early promotion for the film," Rogen joked when we caught up with the actor at SXSW. "I know we'll get a lot of hits online. Get the name out there. I call Jared... From Just Jared."

In the movie Rogen plays a happily married father of one living a peaceful life with his wife, played by Rose Byrne. Things get turned upside down when a fraternity run by Efron's character moves in next door, leading to an increasingly dangerous battle of one-upmanship.

And as an extra feature for fans, Efron is often seen missing his shirt... But he's not the only one.

"I'm shirtless more in the movie than I wish I was!" Rogen recalled, laughing. "The ratio is off, the Zac to Seth shirtlessness. It's like, one to one. That's not what you want. It should be 50 to one!"

That wasn't always the case on set, though. When Efron fist showed up for filming a scene set in a major clothing store chain, he was worried the entire shoot would find him sans outerwear.

"The second day of filming was Abercrombie and Fitch," Efron said. "I was standing there going, f--k this is my nightmare. This is very well what could happen to me some day."

"It was a little too real," quipped Rogen.

Luckily for Efron, later that day he wasn't the only one who lost his shirt, as Rogen got into the topless game.

"And then Seth was there, and it was cool," Efron continued.

"Then it became my nightmare," Rogen shot back.

Making matters worse, though was that customers kept trying to actually buy clothes while the shoot was going on; only escalating Efron's nightmarish situation. That said, he did eventually manage to get that avenue of ingress shut down.

"Real people were walking by, they were trying to get them into the store... Nobody was coming into the store!" Efron said laughing.