Despite being a part of the X-Men cinematic universe, the Deadpool franchise has always played fast and loose with the continuity — even more so than Days of Future Past did.
The Merc' With the Mouth's movies constantly play up the comic book ties that the main X-Men films tend to ignore, and that trend continued with Deadpool 2 and the appearance of a classic villain.
Warning: Minor spoilers for Deadpool 2 below.
The character previously appeared in X-Men: The Last Stand, but there was nothing there to indicate Cain Marko had a familial relationship with the mutant leader Professor Xavier.
But Deadpool 2 makes it explicitly clear that the two are brothers, confirming the bond from the comics has been extended to Wade Wilson's corner of the cinematic universe. In the movie, Julian Dennison's character Firefist helps break Juggernaut out from his incarceration, and in return he will help the young man murder an abusive headmaster from the home where Firefist used to live.
As Juggernaut and Firefist approach the group home, the young boy asks the villain about his iconic helmet, asking if it's because "your brother tries to read your mind?"
Juggernaut responds by saying yes, but Professor X is in a wheelchair so they're "even."
While the ableist joke is kind of in poor taste, the aside is another example of how the Deadpool franchise relishes in the weird, expansive source material of the X-Men comic books, where as the mainstream movies tend to shy away in order to stay "cinematic," for lack of a better word.
The movie also makes an overt mention of Mojoworld, the TV-obsessed planet presided over by bizarre X-Men villain Mojo. In the sequence where Shatterstar responds to a Craigslist (or LinkedIn) advertisement about X-Force, he namedrop the planet and refers to himself as an alien. This fact is further driven home when he unceremoniously gets chopped up by helicopter blades, and his green blood splatters around.
For fans who need everything to line up, the continuity to be perfectly plotted, and for every reference to sync up to the timeline, Deadpool 2 might be maddening. It doesn't attempt to fix or clear anything up, instead relishing in the fact that it can do what it wants.
But that's a part of the appeal of the franchise, knowing that it's a superhero movie and doesn't need to take itself seriously.
Deadpool 2 is now playing in theaters.