X-Men: 10 Theories For How They Can Join The Marvel Cinematic Universe
3. Nick Fury Has Been Keeping Them In The Shadows
Nick Fury is a great ally to Earth's Mightiest Heroes, but don't forget that he was the one who used Agent Coulson's death to manipulate them into assembling in The Avengers. Since then, Marvel Studios seems to have shied away from exploring his shadier side, but it's still not that hard to believe he's somehow covered up the existence of mutants.
Why he would do this is hard to say, but it could be that the X-Men have been helping out all this time, only for Charles Xavier to wipe everyone's memories afterwards. How cool would it be to get a series of flashbacks inserting the X-Men into key events before showing Professor X making the likes of Captain America and Thor forget at Fury's request?
There's a risk this could become a tad convoluted, but if mutants really have been out there all this time, it's pretty bizarre to think they've managed to stay hidden, especially when they're often such powerful, colourful characters. After all, since when has Magneto been one to hide from humans?