Although not directly involved in the race to develop the first atomic bomb, Albert Einstein had an unexpectedly significant role in Christopher Nolan's new film. Einstein, who profoundly changed physics and ideas about space and time, once expressed skepticism about quantum physics, which happened to be Oppenheimer's area of expertise. The younger physicist even referred to Einstein as "completely cuckoo."

Their relationship evolved over time, and it was only in the last decade of Einstein's life, after the bombs had been dropped, the war had ended, and both scientists found themselves at Princeton, that they became "close colleagues and somewhat friends," as Oppenheimer recalled in 1965.

Tom Conti, the 81-year-old acclaimed actor portraying the father of relativity theory, previously collaborated with Christopher Nolan on The Dark Knight Rises. However, he has remained silent about his experiences on the Oppenheimer set so far.

Cillian Murphy, who takes on the role of the titular theoretical physicist responsible for ending WW2, described his performance as a once-in-a-lifetime opportunity. “I can’t think of any better word than it’s a dream. It sounds like such a cliché, but it’s the truth. But I had no idea he was going to call me. He just called me out of the blue," he explained to Collider. "It’s a big shock, and a very pleasant one, but then you kind of go, ‘Okay, now I have a lot of work to do.’”

Murphy, who is an old timer in the 'Nolanverse', has been vocal about the physical and mental challenges his preparation for the role demanded. He disclosed to The New York Times that he shed "quite a bit of weight", for a time only eating an almond a day, to accurately portray Oppenheimer's slender appearance, almost emaciated.

"I was running on crazy energy; I went over a threshold to where I was not worrying about food or anything. I was so in it, a state of hyper-something. But it was good because the character was like that. He never ate,” Murphy reflected on the preparation for his already iconic role to the Guardian.

According to Murphy and the Pulitzer-winning biography, 'American Prometheus', which inspired the film, Oppenheimer sustained himself with minimal intake, primarily relying on Chesterfield cigarettes and double-strength martinis, with lime-dipped rims.

Rami Malek, who plays physicist David Hill, meanwhile only appears in the film for several minutes, and yet he makes the most of it. He mostly appears alongside Dr. Enrico Fermi, whose team is tasked with creating the nuclear reactor, trying to convince Oppenheimer to support the Szilárd petition, signed by 70 scientists and later sent to President Truman as a protest against bombing Japan. The two times that this occurs, however, Oppenheimer knocks Malek’s hand away in frustration.

It’s a humbling role for the Oscar-nominated actor who's known for his role as Queen's Freddie Mercury, as he is seen primarily as a minor annoyance in his scant appearances. Although Malek is yet to speak about his time playing Dr. Hill, audiences are already in awe of that one scene of his.