Yeah, we know, you wish Deadpool had shown up in X-Men: Apocalypse because it would have made the movie better. You're probably right, but maybe this will help. Ryan Reynolds' Deadpool basically hijacked a Japanese trailer for X-Men: Apocalypse with a post-credits scene, totally in English, in which he snarkily gives fans a special countdown of things to look forward to.
So wait, why does a trailer have a post-credits tag? Well, Deadpool goes on to explain that, and his answer is a direct jab at 20th Century Fox movies. Ahhh, Deadpool, never failing to slice the hand that feeds him.
Check it out below. Deadpool pops up after the trailer is over, obviously.