4. Disappearing Characters
Admittedly, this isnt so much of a discrepancy as it is an annoyance, but the X-Men films have seen a host of characters vanish from proceedings in between releases for no apparent reason whatsoever. The most notable of these is perhaps Alan Cummings Nightcrawler, who was featured prominently in X2 but was absent (and not even mentioned) during X-Men: The Last Stand, owing to the fact that Cumming declined to reprise the role because of the lengthy daily makeup application sessions that it required. Before him, there was both Sabretooth and Toad, who appeared as henchmen of Magneto in the first film but were not present in the sequels. Both endured defeat at the hands of the X-Men, but their injuries were seemingly not major enough to result in their maiming or deaths, making their subsequent absences somewhat inexplicable. With the upcoming release of X-Men: Days of Futures Past, it seems that this will become an issue again, as the merging of two timelines has necessitated a cull of several supporting characters, many of which were therefore pointlessly developed in X-Men: First Class, such as Emma Frost, Azazel, Riptide, Banshee and Angel Salvadore.