[WARNING: Major SPOILERS for X-Men: Days of Future Past in this Article!]
X-Men: Days of Future Past is now theaters, bringing with it the promise of a (semi-)rebooted X-Men Movie Universe where the missteps of past films will be course-corrected (or outright wiped away) in favor of providing the franchise with a clean slate on which to build toward a bigger, better, "fewcha" (future).
Of course, throughout the marketing campaign for Days of Future Past, hardcore fans of both the X-Men comic books and/or films have remained wary of the lingering issue of continuity errors. The six films in the preceding X-Men movie saga (X-Men, X2, X-Men: The Last Stand, X-Men Origins: Wolverine, X-Men: First Class and The Wolverine) have nearly choked themselves to death with inconsistencies and contradictions in shared universe storytelling. It was an annoyance in the past, but it is a downright deal-breaking flaw in the era of shared universe franchises.
As we stated in our official X-Men: Days of Future Past review, the film does a lot of good things for the franchise - but that doesn't mean it is able to completely clean up the messy continuity. Granted, Days of Future Past manages to negate the other X-Men movies (with the exception of First Class) in favor of a much-needed mulligan; but how well it earned that second chance at better continuity is up for debate.
We selected some of the biggest and most glaring continuity issues in Days of Future Past - and some additional ones that meticulous viewers will no doubt notice and likely criticize, even as the franchise tries to leave its ugly blemishes behind.
Prof X. Lives
One of the biggest continuity issues that has been apparent ever since Days of Future Past was first announced was the return of Patrick Stewart's Professor X. In X-Men: The Last Stand, Professor X was vaporized by Dark Phoenix/Jean Grey - only to achieve resurrection by transferring his consciousness into the body of a comatose patient who was under the care of Moira MacTaggert (as seen in a post-credits scene):
Now, if you read around the Interwebs, you'll hear all kinds of justifications for how Xavier's resurrection could result in what we see in DoFP - and also the post-credits scene of The Wolverine, which serves as a direct lead-in to DoFP. The most popular theory is that when Xavier transferred his consciousness, he did so into the body of a twin brother. This familial relation is never specified in X3, but it isn't impossible (just soap opera-style cheesy). However, even it that WAS a viable explanation, it still wouldn't explain how or why Xavier's twin brother also ended up paralyzed and confined to a wheelchair.
At the end of The Wolverine, any direct explanation is left to vague references, as Wolverine asks "How is this possible?" upon seeing Xavier alive, and Xavier answers, "You're not the only one with gifts," suggesting that some aspect of his powers has allowed him to cheat death. A lot of fans hoped that Days of Future Past would detail exactly how Xavier made it back, but alas, that explanation is nowhere to be found. And since DoFP insists that X3 is official canon, that unanswered question is certainly a big one.
Future Wolverine's Adamantium Claws
Days of Future Past clearly recognizes the events of both X-Men: The Last Stand and The Wolverine, and when last we saw Logan onscreen, his Adamantium claws had been destroyed in a battle with the "Silver Samurai." From early marketing of Days of Future Past, the question of how Future Wolverine got his claws repaired was nagging the minds of fans everywhere. In the actual film, we get zero explanation of how this particular restoration occurs.
Director Bryan Singer promised all would be revealed. The easy answer seemed to be having Ian McKellen's future Magneto be the source of Wolverine's re-attachment to his famed metal; all it would take is a throwaway line of dialogue and the whole thing could be settled.
The most we get from the film is implication: In the 1970s, young Magneto (Michael Fassbender) reveals the imaginative vision for endowing Wolvie with a metallic upgrade, as the pair are on a jet flight to Paris. You could call that an implied explanation, but most fans would, in turn, call B.S.