Due to the nature of the characters, all filming had to be done at night. This placed a tremendous strain on scheduling as most shooting was done solely on the weekends. In total, about 60 hours of filming occurred over the course of 6 days.
During the introduction, the ticker tape on the bottom of the screen mentions a heroine group that is believed to work with Batman. This is referencing the Birds of Prey, indicating that they exist in this universe.
During the first night of filming, a bat flew about on set. The production team saw it as a blessing.
Pyg was not the original villain. In fact, the original script was just a monologue. The writer felt that Pyg would be the perfect villain given the tone the script eventually assumed and the character's popularity in Rocksteady's "Batman: Arkham Knight," which released shortly before the script was finalized.
The vast majority of the cast and crew are all from Michigan, save James Matthew Fuller (Tim Drake) who is from Chicago.