10 Movie Mysteries FINALLY Explained

One of Zack Snyder's Justice League's final scenes sees Bruce Wayne (Ben Affleck) have an apocalyptic dream - a "Knightmare," even - where Darkseid (Ray Porter) has conquered Earth and Superman (Henry Cavill) has become a dangerous renegade.

Batman has teamed up with heroes and villains alike to resolve the situation, most surprisingly even striking a truce with The Joker (Jared Leto) - albeit an incredibly uneasy one.

Quite why Batman would ever join forces with the Clown Prince of Crime, and what a power-less Joker could possibly offer him, are left totally up in the air during the brief sequence.

But on a recent panel at the SnyderCon 2023 event, Snyder revealed that The Joker is the only person who knows where the Kryptonite is which can be used to defeat Superman.

In Snyder's own words - "If [Batman] kills him or gets rid of him, then he's screwed himself."

There you have it. While the DCEU is effectively dead once Warner Bros. burns off the remaining projects, it's nice to know why the Dark Knight forged an (admittedly iffy) alliance with his arch nemesis.