08/05/2011 05:52 pm ET | Updated Oct 05, 2011

Ryan Reynolds' Mom Witnessed His Lorno On 'The Change-Up' Set (VIDEO)

In the upcoming gross out body switching comedy, "The Change-Up," Ryan Reynolds' bon vivant struggling actor character Mitch gets put into the body of Jason Bateman's family man lawyer character Dave, which, long story short, means that Reynolds spends much of the film acting like a nice guy. The kind of guy, you might say, you could take home to mom.

Unfortunately, the one day his mom came to set, Reynolds had to get raunchy.

Speaking Thursday night on "Late Night With Jimmy Fallon," Reynolds relayed the embarrassing tale of what took place when he flew his mom to Atlanta so that she could watch a day of filming. That day, of course, ended up being the day he had to play-act in a 'lorno.' Which, for those unaware, means light porno -- think Skinemax, for example.

Even worse, the lorno involved an elderly porn star and a gentleman who was unaware that Reynolds wasn't who he thought he was. To say the least.

"I never look at the advanced schedule on a movie, and this was the one day, I flew my mom in... and there's like a 60-year old porn star in the movie, she takes her top off and the things are just like Marty Feldman, one eye is this way, one that way," Reynolds remembered. "And I was just like, 'Mom, I don't blame you for this, mom, you have nothing to do with this.' It was just horrifying. My mom almost passed away right there on the set."

Reynolds and Bateman recently recorded a wildly inappropriate (and hilarious) promo for the film, which you can see here; to read Bateman's take on the raunch-fest, click here.