In The Killing Joke, Ace Chemicals is the site of an incident that led to a failed comedian-turned-reluctant thief becoming the Joker after a showdown with a young Batman.
For those who know the Joker’s story from The Killing Joke, the sign is a big deal.
For those unfamiliar with DC Comics lore surrounding the Joker, the shot of Ace Chemicals’ sign glowing green in the darkness might have seemed creepy, but not particularly significant.
Unsurprisingly considering its title, the next episode will visit the Ace Chemicals factory.