Robert Downey Jr was rejected as a possible choice for Iron Man multiple times, and getting him hired for the part was an uphill struggle.
As synonymous as he is with the role of Iron Man, there was once a time when Marvel refused to hire Robert Downey Jr to play the superhero. Current studio president Kevin Feige and director Jon Favreau have both spoken about how difficult it was to get Marvel to cast Downey in the role.
During a 2019 panel discussion at the New York Film Academy, Feige spoke about what a risk hiring Downey was. He said, "I remember speaking to the marketing team at Paramount, because Paramount released [Iron Man], saying that if we did our job, Tony Stark will be as famous as Iron Man; Tony Stark will be as well known and as much of a household name as Iron Man because that's how interesting the character has to be."
Feige added, "Literally, the first decision I made and was allowed to make and allowed to try to pursue as president of Marvel Studios was casting Robert Downey Jr. and it felt fun to do that because we knew it'd either be great or the biggest dumpster fire ever. There's very little wiggle room. It ended up being great and I've always said 'No RDJ, no MCU.'"
Downey first played Iron Man in 2008, and ended his tenure in 2019 with Avengers: Endgame. During this time, he went on to become one of the highest paid actors in the world.
Favreau, who directed the first two Iron Man movies, said according to CinemaBlend, "It was my job as a director to show that it was the best choice creatively… and now the Marvel Universe is the biggest franchise in film history. Everybody knew he was talented. Certainly by studying the Iron Man role and developing that script I realized that the character seemed to line up with Robert in all the good and bad ways. And the story of Iron Man was really the story of Robert's career."