Johnny Depp turned down the role of Doctor Strange due to scheduling conflicts with Pirates of the Caribbean.
Leonardo DiCaprio turned down the role of Robin and Spiderman because he thought both characters weren't "complex" enough for his taste.
Jason Momoa was courted to play Drax the Destroyer in Guardians of the Galaxy, but he gave it up because the role was too similar to the ones he's played in the past. Perhaps he was destined to play the Aquaman, since he absolutely nailed it in that blockbuster.
Matthew McConaughey rejected the role of Ego the Living Planet in Guardians of the Galaxy 2 because he felt like a superfluous part of the Marvel Cinematic Universe. "I like Guardians of the Galaxy, but what I saw was “It’s successful, and now we’ve got room to make a colorful part for another big-name actor.” He said.
Tom Cruise was in talks to play Tony Stark (aka the Iron Man) but lost interest after the drawn-out logical issues.
The Next Three: Turning down a superhero role before eventually playing it.
In an interview, Chris Evans revealed that he declined the role of Captain America twice because he was having "little panic attacks."
Chris Pratt's initial disinterest in the role of Star-Lord was related to a previous bad audition experience. He feared that he might embarrass himself as he did in the audition for G.I. Joe. We all know what happened in the end: he got the part and was perfect for the role.
Brie Larson rejected the role of Captain Marvel because she didn't want the fame that comes with it. She told Entertainment Weekly that she worried too much publicity might limit her career in the future. But in the end she was convinced by the quality of the script and eventually took the role.
Heath Ledger's performance as the Joker was near perfection, but Christopher Nolan originally wanted to cast him as Batman. The actor, however, was not interested at all.
Rachel McAdams declined the role of Pepper Potts due to a scheduling conflict.
We all know Gal Gadot as Wonder Woman now, but more than ten years ago, when the director was Joss Wheaton, Kate Beckinsale was approached to play the superheroine. She rejected the role because she didn't like the script and feared that the Wonder Woman outfit might embarrass her children.
Emily Blunt turned down the role of Black Widow because of a scheduling conflict with Gulliver’s Travels.
The Twilight star declined the role of Lois Lane in Man of Steel because she didn't want to be in another franchise.
The reason that Mel Gibson was not interested in playing Odin in Thor might be that he thought it was too violent. In an interview with Washington Post, he said:" To talk about the violence question, look at any Marvel movie. They’re more violent than anything that I’ve done."
The producers of the 1978 Superman movie offered Paul Newman $4 million to be in the movie in any capacity, but the actor was determined he was not interested in playing any DC character.
Joseph Gordon-Levitt turned down the role of Starlord because of a scheduling issue.
Jake Gyllenhaal was offered the role of Rick Flagg in Suicide Squad but declined it for unknown reasons. The actor has since got a second chance at being a superhero and will play Mysterio in Spider-Man: Far From Home.
Jude Law said "no" to the role of Superman because he believed the legendary all-American character should not go to an Englishman like himself. Also, during an interview, Law exclaimed "No Way" when he imagined himself "In that (Superman) costume on posters all around the world".
Joaquin Phoenix turned down the role of Hulk and Doctor Strange because he didn't want to be in too many big-budget films and he thought both roles were not "fulfilling" enough. Anyhow, he will play the supervillain in the film Joker this year.
The reason the Irish actress turned down the role of Scarlet Witch is still unknown, but people presume it to be her busy schedule at the time when director Joss Whedon was casting for Avengers: Age of Ultron.