Director Jon Favreau says that when he began working on the first movie, he had no idea how to make Stark seem real. That's when Robert Downey Jr. told Favreau the two needed to sit down with Musk. "Downey was right," Favreau wrote. "Elon is a paragon of enthusiasm, good humor and curiosity - a Renaissance man in an era that needs them." In Iron Man 2, Musk played himself in a brief scene.