Doomsday? A cryptic post has fans buzzing, but his addition could create problems for Marvel. Find out what challenges a PG-13-rated Avengers movie could face with Deadpool in the mix.

If Ryan Reynolds' Instagram tease is to be believed, there's a chance Deadpool could pop up in Avengers: Doomsday. But what would that actually look like?

For now, Marvel is believed to only be shooting scenes for Doomsday, with the timing of Reynolds' post strongly suggesting he's set to return for that, rather than later down the line. Indeed, some fans are eagerly anticipating a second big reveal of Avengers: Doomsday cast members, perhaps via a second set of chairs, as production continues.