The Death of Robin
Robin’s death is finally addressed with one of the coldest lines in the entire epilogue: “I’m happy to discuss in any way you like, why you sent a Boy Wonder to do a man’s job?” the Joker asks Batman. This is in reference to a couple of things. The vandalized Robin suit displayed in the Batcave is a stark reminder of what is likely Bruce’s biggest failure in this universe, but we’ve never actually learned how the Boy Wonder died despite the references to the meteoric death sprinkled across Snyder’s earlier DCEU work. We know the clown did it but not how (perhaps for the best) or the events that led up to Robin’s death.
But that single line of dialogue delivered by the Joker suggests that some version of the 1988 comic book storyline “Death in the Family” has happened in this universe. In those comics, Robin (the second one, Jason Todd) goes off on his own to find his biological mother against Batman’s wishes, and instead comes face to face with the Joker, who murders him in extremely gruesome fashion. It’s a death that haunts Bruce as much as the deaths of his parents, which Leto’s Joker also references, along with Batman’s real name.
Batman Must Die
Most importantly, the epilogue seems to exist so that the Joker can plant a seed in Batman’s head: only his own self-sacrifice will be enough to stop Darkseid once and for all. This is a storyline that Snyder had planned to explore further in future Justice League sequels, a proposed trilogy that would have culminated with the Dark Knight’s death and the rise of a new Caped Crusader.
It’s unlikely that we’ll ever see this trilogy now that Snyder and the DCEU are parting ways, but the epilogue leaves the road clear for a sequel nonetheless, with Joker alluding to a time-travel plot that would involve Batman’s new crew going back in time to undo Lois Lane’s death and Superman’s villainous turn.
The DC Comics Inspirations
This is hardly the first time the Dark Knight and the Clown Prince of Crime have joined forces to fight a greater evil. Most recently, they’ve teamed up in the DC comics by Scott Snyder and Greg Capullo, particularly in Dark Nights: Metal and Last Knight on Earth, post-apocalyptic stories set in nightmarish wastelands that the director might have at least skimmed while writing this epilogue. In both of these stories, Joker is a key part of Batman’s ultimate victory. In Last Knight on Earth, Joker even finally become’s his “best friend”‘s sidekick.
But in terms of what inspired the grungier look of Justice League‘s Joker, it seems that the filmmaker and Leto went back to the Grant Morrison era of the character for inspiration. Just as Morrison and Tony Daniel’s “reborn” Joker was a clear influence on Leto’s get-up in Suicide Squad, the jarring butcher (?) costume worn by the clown in the epilogue might have been inspired by a similar look introduced in Morrison’s Batman and Robin series (above). Either way, it’s a very odd fashion choice when you’re about to go fight a New God, but then again, Joker isn’t exactly your average dresser.