Many characters come and go in Oppenheimer, and there are plenty of cameos that cause a major impression on the audience. More than just small characters who appear to say one or two lines, these characters are highly impactful to the story despite their brief screen time, and no better way to impact viewers than casting renowned movie stars to take over these roles.
Oppenheimer is one of Christopher Nolan's most ambitious projects and covers the real-life story of the controversial J. Robert Oppenheimer, the mastermind behind the creation of the atomic bomb. Following Oppenheimer from his younger years until the aftermath of World War II, the extensive set of characters and the powerful cameos add up to a rich, nuanced narrative around one of the world's most complex historical figures.
James D'Arcy as Patrick Blackett
James D'Arcy appears right at the beginning of the film as Patrick Blackett, a ruthless professor whom Oppenheimer attempted to poison during his academic years. Blackett was a renowned British experimental physicist, graced with a Nobel Prize in 1948 for his impressive discoveries in the field of cloud chamber research and cosmic radiation.
Despite his scandalous act at the beginning of the film, Oppenheimer appears to feel great admiration for Blackett when he reappears in the film some years later. D'Arcy is better known for his role in Cloud Atlas and previously appeared in another war movie from Nolan, Dunkirk.
Related: How This 1989 Atomic Bomb Creation Film Compares to Oppenheimer
Kenneth Branagh as Niels Bohr
Kenneth Branagh is a prolific director and veteran actor who starred in many of his own movies, including Hamlet and Henry V. Oppenheimer marks his third collaboration with Nolan as he takes over the role of Niels Bohr, a Danish physicist and Nobel Prize winner portrayed as an expert on atomic structure and quantum theory, therefore one of Oppenheimer's idols.
At the beginning of the film, Bohr and Oppenheimer meet at Cambridge and the physicist almost eats Blackett's poisoned apple. Bohr has another major cameo in the Christmas sequence set in Los Alamos, in which he advises Oppenheimer about the bomb, but claims he won't be assisting them in their tests.
Matthias Schweighöfer as Werner Heisenberg
Werner Heisenberg was one of the most brilliant minds of his time and planted a necessary seed of uncertainty in the physics field by coming up with pioneering theories around quantum mechanics. Since Heisenberg was a German, his genius turned him into a looming menace when World War II kicked off: in Oppenheimer, the Americans didn't know how cooperative Heisenberg would be towards the Nazis and the tension about building a bomb first was through the roof.
Matthias Schweighöfer plays Heisenberg when Oppenheimer meets him by chance in Göttingen; two brilliant men who immediately strike up a friendship before the war turned them into enemies. Schweighöfer is a German actor but stars also in American productions such as Army of the Dead and Valkyrie.
Casey Affleck as Boris Pash
Casey Affleck features one of Oppenheimer's most anxiety-inducing scenes as Boris Pash, an American military with a special dislike for communists. Oppenheimer briefly touches on Pash's turbulent background; the son of a Russian priest, he would join the White Army and fight against the Bolsheviks, becoming a hardcore anti-communist military in America.
In the film, Oppenheimer doesn't know anything about Pash when he's interrogated by him; on the other hand, Pash knows every detail of Oppenheimer's controversial file. The result is an unnerving face-off in which every word said could put those Oppenheimer swore to protect in danger, consequently sealing the fate of his dear friend Chevalier.
Rami Malek as David Hill
When Rami Malek first appears as David Hill, he seems to be just a clumsy academic trying to make a difference in the debate around the ethics of the atomic bomb, attempting to persuade Oppenheimer to sign his petition. Later in the film, Malek becomes an absolute scene-stealer when Hill takes a pivotal role in Strauss' Senate hearing, exposing the chairman's personal vendetta against Oppenheimer. In real life, Hill was an associate experimental physicist at the University of Chicago's Metallurgical Laboratory.
James Remar as Henry Stimson
James Remar plays Henry Stimson in Oppenheimer, the Secretary of War appointed by former President Franklin Roosevelt and the key player in the atomic bomb program at the end of World War II, advising President Truman to use it and directing the Hiroshima and Nagasaki bombings.
He appears once in Oppenheimer in a scene that will definitely give rise to heated discussions: Stimson summons Oppenheimer, generals, and other influential war figures to discuss where's going to be the target of the atomic bomb, treating the subject with outrageous indifference and taking Kyoto off the list simply because it was the place he went with his wife for honeymoon.
Related: Oppenheimer: Best Performances in the Movie, Ranked
Gary Oldman as Harry S. Truman
Although President Harry S. Truman is mentioned multiple times throughout Oppenheimer's 180 minutes, he only appears in person once, during a face-to-face meeting with Oppenheimer in the aftermath of the Hiroshima and Nagasaki bombings. As Oppenheimer tries to explain the dangers of further uses of the atomic bomb, Truman dismisses his concerns and calls him a "crybaby" behind his back.
Truman is played by veteran actor Gary Oldman, and it isn't the first time the actor plays major historical figures in cinema: in JFK, he impersonated the infamous Lee Harvey Oswald, and in 2017, he played Winston Churchill in Darkest Hours, an iconic performance that earned him an Oscar, and also Herman Mankiewicz in Mank, the man who co-wrote Citizen Kane's screenplay.
David Dastmalchian as William L. Borden
David Dastmalchian makes a quick cameo as William L. Borden, an American lawyer and a former member of the United States Congress Joint Committee on Atomic Energy. In Oppenheimer, Borden unites forces with Lewis Strauss in an attempt to sabotage Oppenheimer's security clearance, holding the knife of a bureaucratic scheme by filing an extensive complaint against the father of the atomic bomb.
Alden Ehrenreich as Senate Aide to Lewis Strauss
Alden Ehrenreich gets his time to shine in Oppenheimer's third act, playing the role of a senate aide to Lewis Strauss. Through his conversation with Strauss, viewers finally learn that Strauss was the one pulling the strings of the scheme to destroy Oppenheimer's political influence. His position as senate aide prevents him from disclosing the truth to authorities, but his expression after Strauss' defeat says everything he thinks about the farse.
Tom Conti as Albert Einstein
Tom Conti features the most important cameo in Nolan's epic historical drama, taking over the role of renowned scientist Albert Einstein. In the film, Einstein is already at the end of his career, contemplating the consequences of his legacy in a world shattered by another World War. Away from the action, he's merely an observer, and sometimes, a mentor, although he doesn't seem interested in being one.
Einstein appears in two of the film's pivotal moments: first when Oppenheimer comes looking for advice regarding a possible chain reaction that could ignite the atmosphere. Einstein's last appearance occurs when the two reunite in the aftermath of World War II, a moment replayed multiple times throughout the movie and seen from different perspectives; it's only in Oppenheimer's very last scene that viewers get to see what Oppenheimer says to Einstein that hurt him so deeply.
