20. Sigourney Weaver Was Almost Emma Frost
Back when Bryan Singer was still going to direct X-Men 3, he had intended to include the White Queen as a major character, according to X2 screen-writer Dan Harris, who also confirmed that Singer had identified the Alien franchise lead as his intended actress for the role:
We were going to do X-Men 3 for a little while and our big secret or coup was and its not going to happen so its OK we wanted to have a character that was Emma Frost, a famous X-Men character. Shes called the white queen. We were going to ask Sigourney to be it. She was an empath in our version of the movie which means she could control peoples emotions.
It's likely the character would have been a lot different to the version who eventually made it into First Class, but this definitely feels like one of the most unfortunately missed opportunities in the X-Men franchise.
Ultimately Singer bailed to do Superman, Brett Ratner came on board, and we got a film in which Vinnie Jones thinks he's Orson Welles thanks to the silliest line in comic book movie history, and which threatened to kill the X-Men completely. Good choices all round then.