FOR someone once described as America's funniest man, Steve Carell has taken a very dark and disturbing turn.

The 52-year-old, best known for his comedic performances in The 40-Year-Old Virgin, Anchorman and the The Office US, dons prosthetics to portray eccentric multi-millionaire and murderer John du Pont in new big-screen flick Foxcatcher.

Directed by Bennett Miller, the drama tells the true-life story of du Pont, an heir to the immensely wealthy American dynasty, whose friendship with wrestling brothers Dave and Mark Schultz (Mark Ruffalo and Channing Tatum) ended in tragedy.

A few years after shooting Dave at close range, du Pont died in prison in 2010, aged 72.

Carell's creepy look for the film was so effective that even his co-stars would distance themselves from him.

"The prosthetics influenced my performance more than I anticipated," admits Carell. "Once all that make-up went on, people reacted and responded to me differently.

"He did have a very specific way of talking and a certain demeanour, and a specific look as well. His physicality was very off-putting to many people - people naturally wanted to be separate from me."

Being so alienated on set was "different", but the actor is certain it helped him tap into du Pont's complexity.

"I didn't get to know Mark or Channing at all while we were shooting, and it wasn't until much later on, when we were promoting the movie, that I got to know them personally," he adds.

Carell - who started out in Chicago comedy troupe The Second City, which counts comics Tina Fey and Mike Myers among its alumni - has already received awards for his performance, alongside Tatum and Ruffalo, as well as Golden Globe and Screen Actors Guild nominations. There's also a strong Oscars buzz.

Du Pont is certainly Carell's darkest role to date, but he insists it wasn't planned to move into serious parts.

"I was surprised to be asked to meet with Bennett," he says. "I wasn't actively pursuing this movie."

"It was scary, because it wasn't [like] anything I had done before," he continues. "I thought it was a good choice, because whenever you're a little bit afraid or apprehensive, that's a sign you should take it on. That's how you grow."

Born in 1938, du Pont had a wealthy but very isolated childhood. As an adult, there's evidence he had paranoid and obsessive streaks, but he never really explained his motive for killing Dave.

Carell studied du Pont's look, speech and demeanour through video footage. He also met Mark and Dave's widow Nancy and their children.

"He had commissioned a documentary on himself, and the most interesting was the raw footage he didn't want people to see," he says.

"There was a sharper edge to that guy, a less tolerant person and a more abrasive and volatile person.

"He had a very specific idea of how he wanted people to perceive him, and to get a little glimpse of that was helpful."

"I also spoke to people who have worked with and been coached by him. They all had various ideas about who he was, but they all said the same thing about his demeanour and how unnerving he was."

He admits it was a challenge to really get under du Pont's skin.

"It was important I didn't think of him as a villain or monster," he continues. "I saw him first and foremost as a guy who was the personification of his upbringing and his mental state. He was a very sad, damaged human being.

"He was not easy to shake off after filming. It's something I still think about.

"We all felt a great responsibility to the story and to all the people involved."

The Foxcatcher experience has left him keen to take more career risks.

"I would rather do things that are interesting and are possibly a little bit dangerous.

Foxcatcher is now showing in cinemas