Warning: light spoilers for Deadpool 2 below.
Suffice it to say, Deadpool 2 [1] has a lot going for it. With a bangin' soundtrack [2] (that features none other than legendary icon Celine Dion [3]), a pretty wild postcredits scene [4], and the very lucky Domino [5], round two of the growing franchise is delightfully action-packed and entertaining. Then, of course, there are the tons of cameos [6]. Sure, Brad Pitt's small role [7] was easily the most epic, but there's one other surprise appearance that's a direct callback to the first film: all the X-Men!
The moment in question comes while Deadpool is recovering at the mutant academy after attempting to blow himself up. He makes an off-the-cuff remark about how empty the mansion is, and then we pan over to a room with an open door; inside, we see Quicksilver (Evan Peters), Professor Xavier (James McAvoy [8]), Beast (Nicholas Hoult), and even Cyclops (Tye Sheridan). One of them quickly closes the door before Deadpool spots them. The joke is a callback to the first movie, where Deadpool points out that Colossus and Negasonic Teenage Warhead were the only X-Men the studio was able to "get" for his low-budget superhero film.
If you're curious about the real reason behind the massive omission, screenwriter Paul Wernick explained his reasoning [10] for shrinking the cast of characters back in 2016. "We didn't want to populate his world with X-Men. They're two separate franchises, and I think had we done that, we would have been making a mistake. Even if we did have the budget." If you read between the lines, it sounds like a mix of circumstances. Perhaps the first movie really didn't have enough funds to pay for all those high-profile X-Men appearances, so the creative powers that be decided to lean into it. So, we have some "D-list" X-Men in Deadpool, and the antihero himself gets to joke about it.
When it comes to the sequel, there probably was a bigger budget. Even in 2016, though, Wernick wanted to follow the same path. "Going into the sequel, we are embracing this idea that it's a small budget movie," he said. "And we're not gonna populate it with the entire X-Men cast." Since Deadpool is intent on running with jokes as far as they'll go, it all makes perfect sense. And frankly, that funny cameo moment has a way better payoff than a crowded movie with the biggest names of the franchise. We'll take it.