So, there was a rumor for a brief moment in time that 20th Century Fox had added a post-credits scene to Logan that was exclusive to those who saw it in theaters. There was a bit of backlash to that from those who had already seen it, since it doesn't exactly fit the movie's tone or its conclusion. But director James Mangold shot down that rumor, but teased that something special could happen BEFORE the movie, so everybody better get there early. Well, now we know what he was referring to, and it's a doozy. And in case it wasn't obvious enough, SPOILERS!!!!
According to Slashfilm, there will be a Deadpool 2 teaser ahead of Logan, and it will be shot by the sequel's incoming director, David Leitch. Whoa. Thankfully it doesn't feature an appearance by Hugh Jackman or anything (Again, that would have killed the movie's tone), but it plays out like an extended comedy skit involving Deadpool and his feeble attempts to stop some criminals. And it may or may not include a cameo by Stan Lee.
You can check out Slashfilm's report for a full breakdown, but I would suggest just going to see Logan this weekend.