Poison Ivy, Mr. Freeze, and Bane were incorporated into the story due to writer Morgan Evans having been a fan of Batman & Robin (1997) growing up.
This was originally going to be released on Max, but it was removed as part of a tax write off. Amazon acquired the film, and released it on Prime through Metro-Goldwyn-Mayer on December 8th, 2023.
Early drafts had Damian Wayne chasing after a stolen toy of his, but writer Jase Ricci suggested instead having the stolen item be a safety utility belt, as he felt going after the belt symbolized Damian's desire to follow his father's footsteps.
The filmmakers based the Joker on the Snake in The Little Prince (1974), describing him as "the perfect foe to a little kid, because he is basically like a big, peevish child himself - coaxing, cunning, and apt to rapid and irrational tantrums." The animators also made the Joker's design more animalistic and more exaggerated, in order to depict him as over-dramatic.
Carmine Infantino, a comic-book artist who worked on Batman comics during the 1960s-70s appears in the film as a cameo through archive audio. A nephew of Infantino's and longtime friend of director Mike Roth allowed him access to some interviews featuring Infantino, from which Roth selected an audio that he felt worked for a scene in the film.