X-Men: First Class was an awesome comic-book movie. However, the 1960s setting of the film—and the inclusion of certain characters and details—screwed up the other X-Men films' already-established timeline. And there's a hilarious animated infographic that shows it all.
Emma Frost showing up in X-Men: First Class as a bodacious babe when the character first appeared as a teenager in X-Men Origins: Wolverine, which is set a few decades later? Check.
Beast turning furry blue in X-Men: First Class when he's normal in X-2 before turning furry blue again in X-Men: The Last Stand? Check.
And those are just tiny examples of inconsistencies peppered throughout the film.
But the gold goes to Charles Xavier and Mystique growing up together and being BFFs and all in First Class, when they obviously didn't know each other in the other X-Men films.
Have a look!