1. Hes Jason Todd
And finally, one the most-shared fan theories of all time: Jared Letos Joker is actually Jason Todd, a former holder of the Batman sidekick mantle Robin. This would be an interesting adaptation of events in the comics, which began with the Joker battering Jason to death with a crowbar in Jim Starlin's A Death In The Family story. Jason returned to life years later via comic book sci-fi reasons, and began plotting deadly revenge against Bruce Wayne (he was miffed because Bats didnt avenge his death and kill the Joker). He became the brutal vigilante Red Hood, began using deadly force to take on crooks, and fought with Batman several times before making peace with him. The trailers for Batman V Superman - which show a Robin costume hanging in seeming-memorial the Batcave, with an added spray-paint taunt from Joker strongly imply that a version of these events (a game-changing confrontation between the Joker and Robin) has already taken place in the DCEU. But instead of dying, being reborn and becoming the Red Hood, what if Jason Todd was tortured by the Joker into having a total mental breakdown? And what if that led to Jason taking up the mantle of the Joker?
A Reddit user has gone into loads of detail on this, even examining the Jokers tattoos in detail to find clues. Many are willing this theory to come true, believing that itd be one of the bravest and boldest comic book movie arcs. Itd certainly be a fresh take on the material, which is rarely a bad thing. It may seem a little farfetched to me personally, but far stranger things have happened in superhero fiction.
Which Joker theory do you really want to be true? Let us know in the comments