Jim Carrey Had a Gallbladder Attack on Set, Plus 5 More Stories Behind “Dumb and Dumber” as Film Turns 30 (Exclusive)

If you grew up in the '90s, then you probably grew up quoting Dumb and Dumber, the 1994 comedy starring Jim Carrey and Jeff Daniels that also launched the careers of writers and directors Peter and Bobby Farrelly. Some of the most memorable lines?

"I like it a lot."

"Goodbye, my loooove!"

"The first time I set eyes on Mary Swanson, I just got that old-fashioned romantic feeling where I'd do anything to bone her."

As the cult classic turns 30 on Dec. 6, one of the film's stars, Karen "Duff" Duffy, who played the hitman J.P. Shay in the movie, opens up to PEOPLE about what it was like being on set. "It was magic," says Duffy, 62, noting that it was her first major film.

She says everyone stayed at the same hotel in Utah and had an absolute blast together.

"There's a belief that if you're having a great time on set, it's never going to shine through on the film, but this was the one exception to the rule." She's still in touch with Peter Farrelly and plenty of others from the film. Below, she reveals what Jim Carrey was like on set, how the movie nearly didn't get made, and more things you never knew about Dumb and Dumber on its 30th anniversary.

Related: 'Dumb and Dumber' Reunion! Jim Carrey Crashes Jeff Daniels Interview and Lovefest Ensues

It Wasn't Originally Called Dumb and Dumber

Duffy says the movie was originally titled A Power Tool Is Not a Toy. "I still have the original script where that's the title," she says, adding she's not sure when or how it got changed to Dumb and Dumber. "I think just the idea that these characters were such knuckleheads was the inspiration." She notes that it was difficult not to laugh at all of the crazy jokes during filming. "There was such a joy in seeing how silly you could get," she says. "The Farrelly Brothers put all the jokes in."

It Very Nearly Didn't Get Made — but Jim Carrey Elevated the Budget

Duffy says that when she first read the script, she was dying laughing. "I called Pete Farrelly and told him he was a genius," she says, adding that she told him she wanted in on the film. Because she worked at MTV at the time and was connected to tons of stars, she said she tried to recruit people to be in it. "Chris Farley. Matt Dillon. Fisher Stevens. I was telling everyone, 'You have to read this script!' And then when Jim Carrey signed on, it just took off like a rocket." The actor had just done Ace Ventura: Pet Detective and was quickly becoming a huge star. Not long After Dumb and Dumber, he became the first actor in Hollywood to command $20 million a movie.

Jim Carrey Suffered a Gallbladder Attack on Set

"We were filming in the airport one day, and Jim doubled over and was rolling around, and the reaction from pretty much everybody on set was, 'Oh, this is a prank. This is just Jim monkeying around,' " Duffy recalls. "But the medic on set was like, 'Is this for real?' He said 'Yes.' " Duffy says it was a gallbladder attack, and as they wheeled him offset, she asked if she could have his gallstones. "He said okay. I was going to make him a set of cufflinks with them. And then I went to visit him in the hospital, and he told me he'd given them to the girl he was seeing."

People on Set Would Also Quote the Film's Memorable Lines

Duffy says that when Carrey ad-libbed a line that made everyone laugh, the entire crew, from craft services to the teamsters, would star quoting it. "Like, 'I Like it a lot. Everybody on set would be saying that, until he'd ask us to just knock it off." She says that Carrey was warm and kind to everyone, too. "There was such elasticity to his genius," she says. "It just seemed so easy for him. He was easygoing and lighthearted and friendly and kind to everyone. And I loved that everyone knew that Jim was our guy. We were there because of him. This movie got made because Jim said yes to it."

Jeff Daniels Was Always the Choice for Harry Dunne

"Pete knew he wanted Jeff Daniels," says Duffy. "He just said, 'That's the actor that I want.' I think Jeff was worried it would tank his career, but it just shows his range. And I think he did it because Pete and Bobby are such genuinely good, kind, funny crackpots. They put in every joke, and if somebody came up with an idea, they were totally open to it. And I think that's why Jeff Daniels felt so comfortable doing this, even with the bathroom humor."

Related: Jeff Daniels Recalls Filming Dumb and Dumber Toilet Scene and Fearing It Would ‘End’ His Career

Karen Duffy's Role Was for a Man; the Directors Didn't Change That

"I play a male role," Duffy says, noting that she was originally slated for a female part. "Then with the success of Ace Ventura and Jim coming on and being so successful, it elevated the budget. And I remember Pete saying, 'Well, that role had to go to somebody else.' " Duffy says she wasn't upset — she was just glad it was getting made. "I told him it was great he was getting the best people. And he said, 'Well, there's one other role, but it's for a guy.' And I was like, 'Dude, I would do craft services, whatever you need.' And so the character that I play is J.P. Shay, who is named after one of their friends, and it's a male role. They just put me in a dress to play him, and they didn't change any of the words. I'm the associate hitman, and that was not meant to be a female role."

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