16. Emily Blunt Was Almost Black Widow (AND Peggy Carter)
British actor Emily Blunt was Marvel's first choice for not only Black Widow in Iron Man 2 but also Peggy Carter in Captain America: The First Avenger, but she turned both roles down, as she confirmed to New York Magazine.
She said she wasn't attracted to roles in superhero films, because they tend to be "thankless" - where the option is usually the "pill girlfriend" - and she turned down Black Widow and Carter because "the part wasn't very good or the timing wasn't right."
Presumably, Black Widow was mis-timed and Carter too boring, given the requirements of the role and considering Blunt's subsequent revelation that she'd prefer a role in "a comic-book movie or a science-fiction film that would scare the bejesus out of me." It's a shame on both accounts, as Blunt could have slipped into both roles easily, though it would probably have been more intriguing to see her in a more robust action role like Black Widow.