Downey recalls that Nolan, also aware of his actor’s recent streak of MCU movies with Kevin Feige, encouraged him to “work those other muscles.” Indeed, Nolan wanted Downey to stay away from anything he may be known for, or, as Downey described the director saying, “Let’s do it while rendering you devoid of your usual go-to things.”
Those go-to things? Downey knew what that meant:
“It’s the fast-talking, charming, unpredictable, blah, blah, blah, or as my very close friend Josh Richman, a character actor, used to say, I made my bones playing ‘Milo, the offbeat buddy.’ And Milo, the offbeat buddy, better be offbeat!”
Downey has never played a character named Milo, but one can take his meaning. Downey, instead, fell back on an example from his own family. It seems Downey’s grandfather was the same age as Strauss, and he tapped into that image to play his part. He said:
“In doing a bunch of research on Strauss, I connected it to my own grandfather, who would have been a contemporary of his. Robert Elias, whom I never met, was in the U.S. Army, self-made guy. There’s a cool simile between something he was involved in and how Strauss probably felt about Oppenheimer. This grandfather helped do the glass for the Chrysler Building, and the Chrysler and the Empire State were vying to be the biggest. So I was thinking, how can I make Strauss’s competitiveness with Oppenheimer personal?”
A competitive 1950s architect was, some actors might call it, Downey’s key. Once he tapped into that, the resentment of competition between Strauss and Oppenheimer came easily.