If you haven't seen X-Men: Days of Future Past yet, there will be plenty of spoilers below, so read on at your own risk.
In one of his only interviews leading up to the release of X-Men: Days of Future Past, director Bryan Singer addressed the several continuity errors that fans have noticed, including Wolverine's adamantium claws somehow returning after they were sliced off by the Silver Samurai in The Wolverine, and the fact that Trask Industries founder Bolivar Trask is played by Peter Dinklage in this movie and African-American actor Bill Duke in 2006's X-Men: The Last Stand.
Here's what the director had to say about the continuity in X-Men: Days of Future Past.
"Some things you let go. In X-Men: The Last Stand Bolivar Trask was an African-American guy, in X-Men 1 I personally wrote the line that of course I now regret: 'When I was 17, I met a young man named Erik Lensherr' and then in X-Men: First Class I changed that! Some of these I hope the audience will forget about but for the bulk of it I pay attention to the universe."
While some fans may have forgotten about the continuity problems, many others have not, with several different viewpoints surfacing regarding how X-Men: Days of Future Past affects the 14-year franchise, leaving several lingering questions about certain characters and story aspects.
One of the big questions that has lingered since the end credits scene in The Wolverine is how the older Professor X (Patrick Stewart) is still alive, since he was killed in 2006's X-Men: The Last Stand at the hands of the Dark Phoenix/Jean Grey (Famke Janssen). There is a theory that Xavier shifted his consciousness into his twin brother, although that family connection isn't exactly explained.
In X-Men: Days of Future Past's 1973 scenes, Wolverine (Hugh Jackman) still has his bone claws, since he hasn't gone through the Weapon X program that infused adamantium into his skeletal system. However, in scenes set in the year 2023, the metal claws are back, even though the Silver Samurai sliced them off in last year's The Wolverine. Many believe that future Magneto (Ian McKellen) was responsible for the repair of his claws, but it is never fully stated in the movie.
The subject of Wolverine's claws gets even trickier when you take into consideration that the ending of X-Men: Days of Future Past hints that Wolverine/Logan won't even go into the Weapon X program at all. Of course, since Logan can't remember much about his past, it isn't exactly known when he enters this Weapon X program initiated by William Stryker, played by Josh Helman in X-Men: Days of Future Past. It's possible that he goes through the program in the 1980s, when X-Men: Apocalypse is reportedly set, but Wolverine never retracts his claws during the final scene in the year 2023, after the future was saved, so it isn't known if he has the adamantium claws or bone claws.
The last scene takes place in the year 2023, with Wolverine waking up at the Xavier School for Gifted Youngsters in a peaceful future, after the Sentinels have been erased from the timeline. The scene includes Rogue (Anna Paquin), Iceman (Shawn Ashmore), Colossus (Daniel Cudmore), Kitty Pryde (Ellen Page) and the big surprise inclusion of the resurrected Jean Grey (Famke Janssen) and Cyclops (James Marsden). After the Sentinels were destroyed, it created a whole new timeline that is only tied to X-Men: First Class, meaning Jean's death never happened. Badass Digest's piece indicates that the original trilogy, X-Men, X2: X-Men United and X-Men: The Last Stand ceased to exist, after the mutants were revealed to the world decades earlier than in the previous timeline, when Mystique (Jennifer Lawrence) is prevented from killing Bolivar Trask (Peter Dinklage).
With X-Men: First Class taking place in the 1960s, X-Men: Days of Future Past set in the 1970s and X-Men: Apocalypse set in the 1980s, it appeared that this prequel franchise would eventually merge with the original X-Men trilogy, but that doesn't seem to be the case anymore, since X-Men: Days of Future Past created a whole new timeline after the Sentinels were destroyed. The new timeline renders a lot of these continuity errors moot, such as the two different versions of Bolivar Trask in X-Men: Days of Future Past and X-Men: The Last Stand and Wolverine's claws, since it isn't known if the Weapon X program even exists in this timeline.
Several other plot points have been addressed over the past few days, such as how Magneto even got his abilities back to begin with after the events of X-Men: The Last Stand, where a serum removed his powers, the ages when Charles and Erik first meet, and many more. Do you even care about these continuity errors? Are you willing to "forget" about them and move on like Bryan Singer suggested earlier this month?
X-Men: Days of Future Past was released May 23rd, 2014 and stars Hugh Jackman, James McAvoy, Michael Fassbender, Jennifer Lawrence, Halle Berry, Nicholas Hoult, Anna Paquin [THESE LIES], Ellen Page. The film is directed by Bryan Singer.