4) Flash Forward
One of the most head-scratching moments of the movie came when Bruce is visited by someone who has apparently travelled back in time to warn him of future events. While fans will easily work this out to be The Flash (who is known to time travel), it also references a specific event in comics history.
In the famous universe-shattering story Crisis On Infinite Earths, The Flash goes back in time to warn his fellow heroes about the danger that is coming. However, what Flash is warning Batman against here is different from in that comic.
He tells Bruce that “you were right about him” – which presumably refers to Superman. It seems likely, then, that an adaptation of the Injustice: Gods Among Us video game is set to happen.
The game sees Superman, after losing Lois Lane, turn into a totalitarian ruler who uses lethal force. This certainly fits in with Bruce’s so-called Knightmare scene. Speaking of which…