Murphy's co-stars claim he 'didn't eat dinner' on the set of the dramatic epic.
Cillian Murphy's portrayal of J. Robert Oppenheimer, the "father of the atomic bomb," in Christopher Nolan's upcoming epic, Oppenheimer, was an intense undertaking.
The actor's traditionally intense visage is only made more dramatic by the sunken cheekbones and dour expression he wears as the theoretical physicist who led the Manhattan Project during World War II, who seemed to carry the literal weight of the world as he conducted experiments that could lead to the end of humanity.
"When Oppenheimer was running the Manhattan Project and they were doing their calculations, early on they saw the possibility that when they triggered the first atomic device, to test it, they might start a chain reaction that set fire to the atmosphere and destroyed the whole world," Nolan explained to ET ahead of the film's premiere.
"A small possibility, [but they] couldn't eliminate it completely through theory, and yet they went ahead and they pushed that button," he continued. "As a filmmaker, that's the kind of story you're looking to tell."
Murphy is already receiving early Oscar buzz for his leading role, and his castmates told ET that the Peaky Blinders star went so far as to isolate himself on set, forgoing cast dinners and restricting his diet to portray Oppenheimer.
"We invited Cillian to dinner every night and he never went," recalled Matt Damon, who plays Lieutenant General Leslie Richard Groves Jr., the Army Corps of Engineers officer who directed the Manhattan Project for the government.
As for his diet, Emily Blunt, who stars as Oppenheimer's wife, Katherine "Kitty" Oppenheimer, said Murphy was eating, "like, one almond, I think, most nights, or like, a little slice of apple."
"He was losing so much weight for the part that he just didn't eat dinner ever," Damon added.
For his part, Murphy explained that he was just extremely serious about the role.
"They were hanging out," he said of his castmates. "I was in the bath, learning lines."
For a majority of the rest of the cast, on-set camaraderie came fairly easy, as the majority of the shoot was in a remote area of New Mexico -- meaning the cast and crew all stayed at the same hotel and ate at the same restaurant for each meal, leading to something of a "summer camp" atmosphere.
"We had dinner every night," Damon recalled, with Blunt reminiscing, "So many margaritas."
"It was like the dining hall, you'd go in and you'd see everybody and so everyone would just end up sitting together," Damon added. "It always helps when you're kind of immersed with the cast."
Oppenheimer is in theaters July 21.
This interview was conducted prior to the SAG-AFTRA strike, which began on July 13, 2023.
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