If it wasn't for Iron Man actor Robert Downey Jr., Chris Evans may have never joined the Marvel Cinematic Universe as Captain America.
In The Story of Marvel Studios: The Making of the Marvel Cinematic Universe, the story of how Evans ultimately landed his defining role is revealed. While Marvel Studios head Kevin Feige and producer Stephen Broussard were considering Sebastian Stan for the role of Steve Rogers, famed producer Joel Silver summoned the pair to his office. He wanted to pitch Evans for Captain America: The First Avenger as he'd just worked with him on Losers, one of the actor's many comic book roles. As it turns out, Silver had already called Evans and told him he should go out for the part. Then, Downey Jr. did the same thing, which ultimately convinced Evans to audition. But even then, he was hesitant about coming aboard something so big.
"It’s a big commitment to do these Marvel movies," Evans said. "Initially, the offer was nine pictures, then it went to six. But six movies can last a really long time. My concern was the fact that this will be a life-changing experience and the following commitment would be more than I could handle. But that did not turn out to be the case. It was the best decision I ever made."
Stan, of course, didn't land the role. And though he was a bit disappointed, he ultimately decided it was for the best. And his own character, Bucky Barns, would go on to have a significant arc in the MCU -- one that continues to this day, even after Evans' has departed.
The book has been a treasure trove of casting and behind-the-scenes info. Along with the stories of Evans and Stan trying out for their roles, the new book also reveals that Mark Ruffalo initially had the Hulk part locked before Norton beat him out. Of course, Ruffalo would eventually replace Norton and become Jade Giant. Similarly, Chris Hemsworth almost wasn't Thor as he blew his first audition with Marvel Studios. And on the opposite end of things, it was revealed that Zooey Deschanel nearly played the Wasp in The Avengers, which would have prominently featured the hero.
Source: The Story of Marvel Studios: The Making of the Marvel Cinematic Universe