When Deadpool recruits his X-Force team, the list of characters he meets includes one of the biggest movie stars in Hollywood: Brad Pitt, playing a guy called the Vanisher.
Deadpool 2 arrives in theaters carrying at least one major surprise that hasn’t been telegraphed in any of the trailers, teasers, ads, or posters.
The Vanisher later joined an X-Men villain group known as Factor Three, and the Brotherhood of Evil Mutants.
Eventually, he did begin working with the X-Men as a member of X-Force, so his appearance in Deadpool 2 isn’t entirely out of continuity.