By Lindsey Bahr
Updated October 25, 2013 at 04:00 PM EDT

Peter Farrelly knows how much people love Dumb and Dumber. Of course he’s a little more self-deprecating about it than that, and attributes it more to the fact that it’s just always on television. Still, the 1994 Jim Carrey and Jeff Daniels comedy that he created with his brother Bobby was a cultural phenomenon. Has anyone been able to mention Big Gulps or John Denver in the past 20 years without thinking of Lloyd and Harry?

EW spoke to Peter Farrelly, currently shooting the sequel in Atlanta, about two super fans who scored cameos in his movie. One is a guy you’ve never heard of who happened to make a Vine that made the Farrellys laugh. The other is Oscar-winning actress and proclaimed Dumb and Dumber expert Jennifer Lawrence.

This is Trent.

Credit: Lewis Jacobs/NBC

Trent benefited from the fact that the Farrellys love extras and their somewhat recent discovery of Twitter and Vine. For previous films, the Farrelly brothers have auctioned off extra roles for charity. “It’s no skin off our back, and in fact, it kind of helps us,” says Peter. “Any time you get some new extra on the set, they’re so excited to be there that there’s a palpable energy. The crew can feel and the actors can feel and it just makes you happy. You’re making movies and you feel the excitement of it.”

This time, they decided to make it a contest for Dumb and Dumber obsessives to submit a creative Vine of a scene from the movie. They got over 2,000 submissions. Some of them were brilliant. Some vulgar. Some just downright weird. But the brothers couldn’t resist Trent’s video. It was simply the one that made them laugh the most.

“The ones that interested me were the ones that took a very small thing that most people wouldn’t notice,” Peter says. “It was that little wiggle going up the stairs. First he does the double-take before he goes up the stairs but then that little ass shake. I’ve never heard one person mention it, but I’ve always been thinking, ‘What the hell is he doing?'”

That “odd little detail” meant a trip to Atlanta with his wife Samantha (pictured above) to spend a few days on set with Jim Carrey and Jeff Daniels for three scenes.

Lawrence was another story, of course. Oscar winners don’t have to audition over Vine. The Farrellys had offered her a meatier role in the sequel some time ago. Even though she had to turn that down, she knew she’d be in Atlanta shooting The Hunger Games: Mockingjay while Dumb and Dumber To was ramping up production and insisted that they all hang out. So she, Peter and Bobby Farrelly, Jeff Daniels, and a few producers went out to dinner, and then to an Empire of the Sun concert. By the end of the night, Lawrence was telling them how much she wanted to be in the movie. She was even the one who suggested the cameo after the Farrellys politely reminded her of her Hunger Games commitments.

The potential role — to appear as a younger version of Kathleen Turner’s character — was coming up quickly, though. The dinner was on a Friday. They had to shoot the scene on Monday.

“When we woke up the next morning, I figured I was going to get a phone call saying, ‘Look, I’m sorry, I can’t do this. I was out of my mind last night,'” says Peter. “But we did get that call and it was like, ‘This is awesome! I can’t wait to do this!'”

Lawrence’s involvement in the film broke in The Hollywood Reporter almost immediately.”I was disappointed that we couldn’t keep the cap on that,” says Peter, who had hoped that she was so unrecognizable in the film that audiences would only realize it after the fact. But he’s not too distraught about the reveal. That’s what happens when you put one of the hottest young actresses in your movie. “She’s still in it and we had a ball and it’s hard to feel bad about the whole thing,” he says.

“She does know every line by the way,” says Peter. “Everything that Jeff Daniels said would make her giggle. There were little things that he did that reminded her of something from the movie. She would challenge us to name any line and she’d tell us the next five lines. She knew them all.”

Dumb and Dumber To is expected to hit theaters sometime in 2014.

Dumb and Dumber To

  • Movie
  • PG-13
  • Bobby Farrelly
  • Peter Farrelly