Jeff Daniels feared 'Dumb and Dumber' would "end" his career.

Jim Carrey and Jeff Daniels at the Dumb and Dumber To premiere

Jim Carrey and Jeff Daniels at the Dumb and Dumber To premiere

The 69-year-old actor played the hapless Harry opposite Jim Carrey as his pal Lloyd in the 1994 hit comedy, and he's told how he had reservations about the film's notorious toilet scene, in which his alter ego has digestive problems and ended up using a loo that didn't flush properly.

He told USA Today newspaper: “It’s one thing to read the toilet scene, but then the day comes and we’re actually going to do the toilet scene.

“I told Jim, ‘This is either the beginning of my career or the end of it.'”

Jim, who is fearless, told me, ‘It’s going to be great. You’ve just got to go all the way with it.'”

Jim's pep talk inspired his co-star to give his all with the scene.

He said: “That was a couple hours of porcelain gymnastics. And that close-up when they pop in tight on my red face. I had been doing it so long, I had almost passed out.”

The 'Terms of Endearment' star was more known for his dramatic roles at the time and his agents desperately tried to put him off the project.

He said: “I had agents, who weren’t wrong, telling me, ‘You’re a serious actor. This is not the direction you need to be going. We’re going to stop this and get you off this movie.'

“But I wanted to shake it up with a comedy. And I wanted to work with Jim Carrey.”

Jeff knew he had to lean heavily into the more outlandish scenes in 'Dumb and Dumber', particularly because the movie studio had wanted to cast a comedian as Harry.

He said: “It was like, I’ve got scenes. I knew I was going to score.

“If [directors Peter Farrelly and Bobby Farrelly] cut those, the movie was going to be ‘Jim and the other guy.'”

Despite his reservations, being in the movie paid off and the toilet scene in particular was often talked about.

Jeff - who reprised the role in 2014's 'Dumb and Dumber To' - said: “I did my job, beyond my job.

“In terms of comedic scenes, that toilet scene will probably outlive us. It will be funny 40 years from now.”

And even legendary actor-and-director Clint Eastwood was a fan.

Recalling how they met at a celebrity golf tournament, the 'Newsroom' actor said: “Clint says to me, ‘I just saw 'Dumb and Dumber' and you know, the toilet scene? That happened to me.'

“And then he tells a story about dating this woman that he really wanted to impress, but the shellfish hit him the wrong way from lunch.”