In the opening of the episode, when they fight Firefly, that is actually what Firefly originally used to look like and his powers would be rainbow-based. It wasn't until the 90s that he was reinvented as a pyromaniac obsessed with fire.
This story is actually based on a famous Superman story also called Emperor Joker. The difference is that Superman is the main character and Joker becomes Emperor Joker because he tricked Mister Mxyzptlk into giving him a large portion of his powers. It has an amazing premise but the story itself wasn't that good and the episode is much better than the comic in terms of narrative. Again you will see Mister Mxyzptlk both in this show and in Superman The Animated Series. Mister Mxyzptlk is one of my favourite comic book villains ,and yes, like I've said before, his name is hard pronounce.
I know I’ve been saying this a lot recently, but this has to be in the top 10. We got a joker musical Number , a unique take on Harley Quinn, a dive into the psychology of the joker, and a musical number? All of that along with the return of Bat-Mite.
To see the backstory of the production and comic inspirations for the episode, please watch the video from "Casually Comics" titled "Batman Brave And The Bold Goes Insane".
I think the Joker's henchmen in this episode are modeled after famous silent comedians from the 1920's. Looks like Harold Lloyd, Charlie Chaplin, Oliver Hardy and Buster Keaton
Dude after seeing the under the red Batman movie with Jason Todd backstory, this episode was darker with batmite saying the fans choosing what happened to Jason Todd
3:04 yeah, even as a kid, I thought this was cruel! yes I know technically there’s a good chance. Those needles won’t do any lasting damage, but that is legitimate torture.
