When discussing what it was like to work with Cillian Murphy on the set of Oppenheimer, Robert Downey Jr. revealed he felt "iced out" at times by Murphy's performance. Although many celebrities are able to get along, some co-stars just don't work well together for numerous reasons. Cillian Murphy and Robert Downey Jr. worked with an all-star cast on director Christoper Nolan's film, Oppenheimer.

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Robert Downey Jr. has discussed what it was like working with Cillian Murphy on the set of Christopher Nolan's biopic, Oppenheimer. Although Downey Jr. said Murphy was kind behind the scenes, he revealed that the star completely transformed once he embodied the controversial physicist. Robert Downey Jr. revealed that he felt "iced out" by Cillian Murphy's performance as J. Robert Oppenheimer in Christopher Nolan's film, Oppenheimer.

What Robert Downey Jr. Said About Cillian Murphy's Casting In 'Oppenheimer'

Star Robert Downey Jr.
Robert Downey Jr. stars as Lewis Strauss in 'Oppenheimer'.
Via: Instar

Director Christopher Nolan's latest film focuses on J. Robert Oppenheimer, the real-life man who is known as the father of the atomic bomb. Playing the titular role is Peaky Blinders star Cillian Murphy, who has worked with Nolan on multiple other projects, including The Dark Knight Trilogy and Inception.

Starring alongside Murphy is an incredibly talented cast, including Emily Blunt, Matt Damon, Rami Malek, Florence Pugh, Josh Peck, Casey Affleck and Josh Hartnett, and more in the star-studded cast. Nolan was also excited to work with Robert Downey Jr., and has called him "one of the greatest actors of all time."

Sitting down for an interview together, Cillian Murphy and Robert Downey Jr. discussed the film with Extra TV. During the interview, Downey Jr. discussed his co-star's performance.

Downey Jr. also said he felt Murphy was perfectly cast. He said, "I thought it was great, the way Chris (Nolan) chose expertly to cast this guy. It's literally a generation-defining performance."

Related: Cillian Murphy Stole The Role For Peaky Blinders From Jason Statham With One Eerie Text To The Creator

The Sherlock Holmes actor has also discussed what it was like to work with Murphy. It seems the two seem to have got along well behind the scenes, and Downey Jr. had good things to say about his Oppenheimer co-star as an actor and a person.

However, it seems Downey Jr. might have also been shocked by Murphy's transformation into the controversial Oppenheimer, stating his performance made him feel "iced out".

Robert Downey Jr. Felt "Iced Out" By Cillian Murphy's Performance

Star Cillian Murphy
Cillian Murphy plays J. Robert Oppenheimer in director Christopher Nolan's film, 'Oppenheimer'.
Via: Instar

Robert Downey Jr. was excited about the opportunity to work with the successful director, Christopher Nolan on the film Oppenheimer. Downey Jr. has had his ups and downs throughout his career, but made a major comeback playing Tony Stark/Iron Man in the MCU.

During his time in the franchise, he appeared in and promoted multiple films, and the busy star didn't have a lot of time to focus on other projects. When Christopher Nolan offered him a role in his biographical thriller, Oppenheimer, Downey Jr. was thrilled.

Working with Nolan was exciting for The Avengers actor, and during an Extra TV interview the two did together, Downey Jr. raved over Murphy's Oppenheimer performance. However, he also revealed that when Murphy embodied Oppenheimer, his co-star changed so much that it left him feeling "iced out".

Apparently, Downey Jr. was shocked by Murphy's transformation into his character during filming. He described Murphy as a nice person, but when filming, his co-star seemed to truly become a different person.

During their interview with Extra TV, Downey Jr. discussed what it was like working with Murphy on Oppenheimer. He said, "Even just by the time I was on set, seeing how Cillian (Murphy) had embodied this character, to the point where you go like, 'I feel like I'm practically with the guy.' You can't help but feel a little bit iced out by it."

He discussed how Murphy was an entirely different person once they started shooting, "Now Cillian is so warm, and nice and inviting, but then we'd roll, and I'd feel like he was looking through me like I didn't exist. And I was like, 'That sucks.'"

Related: Robert Downey Jr.'s MCU Salary Was So Huge That Rumors Swirled That He Was Fired For Getting Too Expensive For The Studio

Robert Downey Jr. and Cillian Murphy will likely be at odds in the film. Their characters, Lewis Strauss and J. Robert Oppenheimer respectively, had a conflicting real-life relationship.

Robert Downey Jr. has worked with numerous talented actors in the past, but it seems he might have been taken off-guard by how well Murphy inhabited the man who changed the world.

What Has Cillian Murphy Said About Playing J. Robert Oppenheimer?

Cillian Murphy, Celebrity
Celebrity Cillian Murphy poses for a picture.
Via: Instar

Although Cillian Murphy lives a quiet life, he has played variety of incredible roles, including the brutal gang leader Thomas Shelby in Peaky Blinders. In his upcoming film, Oppenheimer, the star portrays the controversial physicist who changed our world, J. Robert Oppenheimer.

Murphy has worked with director Christopher Nolan on numerous other projects, but the star has said playing the father of the atomic bomb is both "terrifying and exciting".

According to Syfy, Murphy told Empire how he felt about playing the titular role. He said it was "terrifying and exciting in equal measure, which I think is the best place to be as an actor starting off on a project."

The 28 Days Later actor added, "You can't sit back and think, 'I've got this, this is going to be a piece of [cake], I hope the catering is good.' This was like, 'F***.' But then it started, this hunger. I could feel this hunger for the character and for the job."

Nolan said about the lead character, "I put an enormous burden on that central character. There always would have been a big burden with playing this type of person, but to have to carry the whole audience with them... That's when I thought of Cillian."