Christopher Nolan has compared Cillian Murphy's Oppenheimer transformation to Heath Ledger in The Dark Knight.
The 53-year-old filmmaker — whose film starring Murphy as J. Robert Oppenheimer has earned 13 nominations for this year's Academy Awards — recalled seeing him in character for the first time, and he couldn't help but think of the late actor's turn as The Joker in his 2008 Batman movie.
He told Variety: "It was really in the hair and makeup tests, which we shoot on Imax and in black-and-white.
"You start to see the actor bringing an icon to life, putting the hat on, the cigarette in the corner of his mouth. You're starting to see how he moves. It's a thrilling moment.
"It is on every film. Seeing Cillian put this iconography together, it reminded me of my hair and makeup tests with Heath Ledger for the Joker."
Oppenheimer is leading the way for the Oscars, with nominations for Best Picture, Best Actor in a Leading Role (Murphy), Best Actor in a Supporting Role (Robert Downey Jr), Best Actress in a Supporting Role (Emily Blunt) and Best Director for Nolan himself.
The film is also in the running for Best Cinematography, Best Adapted Screenplay, Best Original Score and Best Makeup and Hairstyling, plus nods for Costume Design, Editing, Sound and Production Design.
Meanwhile, Murphy told the outlet that he thinks the real Oppenheimer would be "quite confused, in a pleased way", by the whole project.
He pondered: "I think he'd be happy that if nothing else, maybe people will think about nuclear weapons in a more focused way than we tend to because, you know, half the population on the planet lives in a country that has nuclear weapons and we just don't think about it because there are more pertinent and pressing things going on in our lives.
"But this is there. It's like the sword of Damocles hanging over all of us all the time.
"Perhaps he might be pleased because that was kind of his life's mission, was to be candid about the state that the world is in."