1. The Batman V Superman Trailer
There are two big spots in the Comic-Con trailer which are responsible for creating this theory in the first place. The first is Bruce's line to Alfred as he asks him: "20 years in Gotham, how many good guys are left? How many stayed that way?" That could be reference to any number of supporting characters in the world of Batman (Two-Face for example), but what if he's actually talking about Robin? That's been the prevailing theory since these theories about the sidekick transforming into The Joker came to light, and seeing as the quote above lands around the same time that Robin's costume appears on screen, there's a good chance that the two are connected. The second clue comes in the form of that taunting message sent to Bruce after the destruction of Wayne Financial. It feels personal (especially the mention of "family"), and it would make more sense for it to have come from someone who truly knows Batman...a former sidekick perhaps? That would explain why they would take such a personal dig at Bruce and makes more sense than The Joker being privy to his secret identity. The writing appears to match what can be seen on the suit too, so there's no doubt that this moment was included in the trailer to create speculation about it being from the Clown Prince of Crime, and while there are those who believe that it could have been sent by Lex Luthor as a way of manipulating Bruce, I have to agree that it being sent by Robin makes more sense. Do you think Jared Leto's Joker will be revealed as Jason Todd? Share your theories below in the comments thread.