Jeff Daniels' agents feared Jim Carrey might overshadow him, but why?

Jeff Daniels' agents feared he would be overshadowed by Jim Carrey in Dumb and Dumber.

The 71-year-old actor starred alongside Jim, 64, in Dumb and Dumber, the 1994 comedy movie - but Jeff's agents were initially reluctant for him to commit to the role, fearing he might be overshadowed by his co-star.

Speaking with Hour Detroit, Jeff explained: "I wanted to do comedy, and my agents tried to talk me out of it."

Despite this, Jeff was determined to star in Dumb and Dumber, convinced that it could become a success.

However, the Hollywood star has still been surprised by the movie's box office success and its enduring appeal among film fans.

Jeff - who played the part of Harry Dunne in the hit film - said: "We knew that 12-year-old boys would think it was Citizen Kane, but we weren't prepared for the No. 1 movie for six weeks. I still have the scrapbook of the 200 reviews for Dumb and Dumber, and there's not one good one."

Dumb and Dumber was a commercial success, grossing $247.3 million against a $17 million budget.

However, at the time, Jeff feared that Dumb and Dumber would "end" his career, due to 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.

Jeff 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."

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 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."