Lee Pace was a serious contender for the role of Peter Quill but Chris Pratt was cast instead. Lee went on to play Ronan the Accuser.
Chadwick Boseman initially auditioned for Drax the Destroyer in Guardians of the Galaxy, but the role went to Dave Bautista.
Saoirse Ronan was the “prototype” for the character of Scarlet Witch, but the role ultimately went to Elizabeth Olsen.
John Krasinski was asked to audition for Steve Rogers way before Chris Evans had even been offered the role. At his audition, he was asked to try on Captain America’s suit and as he was pulling it up, Chris Hemsworth walked by and said, “Ya look good, mate.” John joked that he left right after seeing how “jacked” Chris was.
Amanda Seyfried turned down the role of Gamora in Guardians of the Galaxy. She said, “I didn’t want to be part of the first Marvel movie that bombed. I said, ‘Who wants to see a movie about a talking tree and a raccoon?’ Which is clearly — I was very wrong… I remember Jennifer Lawrence talking about once how long it took her to get blue. And I was like, ‘That seems like hell on Earth,’ because then you get to set and you’re only there for a couple hours, and then you have to take everything off. And that was literally the reason.”
Tom Hiddleston originally auditioned for the part of Thor, but was obviously cast as Loki instead.
Danny DeVito auditioned for Rocket, but Guardians of the Galaxy director James Gunn felt that the character needed a younger-sounding voice.
At one point, Sam Rockwell was in the running to screen test for Tony Stark. He didn’t get the part but felt like his Iron Man 2 character, Justin Hammer, was his “chance to be Tony Stark.”
Emily Blunt was Jon Favreau’s first choice for Black Widow, but due to conflicts with the movie Gulliver’s Travels Emily had to drop out.
Jason Momoa was in the running for Drax but he turned it down. He told IGN, “I want my children to see their father happy. It’s not that it’s not a good role, it just wasn’t the right thing. I was on Stargate: Atlantis for four years playing a similar character called Ronon, who was an alien who didn’t say much and grunted. I’ve been there and done that, whether people have seen it or not.”
Yahya Abdul-Mateen II was testing to play M’Baku before Winston Duke was offered the role.
DeWanda Wise was originally supposed to play Maria Rambeau but had to drop out because of her prior commitment to Netflix’s She’s Gotta Have It.
Timothée Chalamet auditioned for Peter Parker and was apparently very stressed during it. He said, “I read twice and I left sweating in a total panic. I called my agent, Brian Swardstrom, and I said, ‘Brian, I thought about this a lot and I have to go back and knock on that door and read again.'”
Matthew McConaughey was offered the role of Ego in Guardians of the Galaxy Vol. 2 but he turned it down to be in The Dark Tower.
Sebastian Stan originally auditioned for Steve Rogers but was told he wasn’t right for the part and was offered the role of Bucky Barnes instead.