During heavy days on the set of Oppenheimer, Cillian Murphy said there was one co-star he knew he could always turn to, who would make him laugh. He called Emily Blunt, who played Oppenheimer’s wife, Kitty, in the film, one of the funniest people he’s met, which helped create a close friendship between them.
Cillian Murphy found Emily Blunt to be one of the funniest people he met
During an interview with the Los Angeles Times, Cillian Murphy revealed a very important rule he has when he’s on set filming. The Oppenheimer actor said he “can’t work unless there’s a lightness around the set,” especially since he takes on more serious roles. “There has to be some levity,” Murphy explained.
He continued, “A lot of the films I do are quite heavy and go to some dark, challenging places, and you have to be relaxed to do that. So I don’t walk around in a state of fucking angst. I need to feel at ease. I can’t be in that dark place all the time. I don’t have the stamina for it.” While filming Christopher Nolan’s summer blockbuster Oppenheimer, where Murphy portrayed American scientist J. Robert Oppenheimer, the lightness was particularly important. 
Cillian Murphy called Emily Blunt, who played Oppenheimer’s wife, one of the funniest people he’s met, which helped create a close friendship between them. “She’s also one of the funniest people, and I have a rule that I can’t work unless there’s a lightness around the set," he said.
Emily Blunt talked about Cillian Murphy's diet for Oppenheimer
Cillian Murphy underwent a significant physical transformation which included losing weight, to portray J. Robert Oppenheimer, the inventor of the atomic bomb. He had to follow a very restrictive diet to drop pounds. Emily Blunt who played his onscreen wife told Extra, "He had such a monumental undertaking. And he could only eat, like, an almond every day. He was so emaciated.”
Matt Damon also told Extra that, "The sheer volume of work that he had, and the level of detail that Christopher [Nolan] demands. There was always something for him to be thinking about. There was something coming down the pike that he needed to." “Be ahead of,” Blunt finished for him.
Cillian Murphy addressed his dramatic weight loss for the role during an interview with IndieWire, saying, “I don’t advise it.” The weight loss was part of an effort to look as physically similar to the real Oppenheimer as possible, a man whom Murphy said lived off “cigarettes and pipes, he would alternate between the two.”
In an interview with The New York Times, he said, “I love acting with my body, and Oppenheimer had a very distinct physicality and silhouette, which I wanted to get right." "I had to lose quite a bit of weight, and we worked with the costume and tailoring; he was very slim, almost emaciated," he added. “He had these really bright eyes and I wanted to give him this wide-eyed look, so we worked on his silhouette and expressions a lot before starting.”
