Christopher Nolan’s script for Oppenheimer called for a massive cast to play the dozens of characters representing some of the most important movers and shakers of the 20th century. Nolan didn’t want to use composite characters for the sake of simplifying things, feeling it was wrong to attribute the significant, signature ideas or innovations of one renowned figure to another. And as his characters would be moving in and out of the story in briskly paced scenes, and sometimes, in meaty cameos, he wanted to make sure that they popped distinctly for the audience and stayed vivid in their mind.