Zack Snyder has been known to leave a trace of easter eggs for fans to dig up, and that seems to have trickled down to other DCEU movies as well. In this case, a DCEU film. Batman Vs Superman featured a displayed suit that previously belonged to Robin, Batman’s longtime sidekick. The suit was covered in neon graffiti with words that read, “Ha ha ha, joke’s on you, Batman!”
Now, any Batman fan can point to one criminal that would write such particular words. The Joker, though not seen in the movie, got a shout out of sorts for why Batman became the way he was in the movie. The Joker was responsible for killing Jason Todd in the comic Death In The Family. But it seems like The Joker might not be Robin’s killer on celluloid.
Suicide Squad started out chaotically to quickly introduce the various players of the film. And when Harley Quinn was first introduced on screen, there was a blink and you might miss it text that said she was responsible for the killing of Robin’s death. Now, given Harley Quinn’s history with the Joker, it may be presumptuous to think that she killed Robin, but she was the Joker’s girlfriend, so she definitely was involved somehow.
Zack Snyder commented on Robin’s fictional death with IGN:
“In my mind, it was that Robin had died 10 years earlier, during some run in with a young Joker (Jared Leto). To me, it was a fun backstory there to play with. The whole idea was that there had been loss and sacrifice. In a weird way, he sacrificed everything to be Batman, right? He doesn’t really have a life outside of the cave. I thought by including Robin — a dead Robin — it would help us understand he’s been on quite a little journey.”