Career Resurrection: Jim Lee was one of the creators who helped usher in independently-owned comics with Image Comics and was a popular artist during The '90s thanks to his work on X-Men. After this though, he fell into relative mediocrity with little to no notable additions to his resume. Then came Hush and his career was revived in a big way, leading to him eventually being granted the position of DC's co-publisher.
Executive Meddling and What Could Have Been: Allegedly, Hush was originally supposed to be a Lazarus Pit-revived Jason Todd, with Tommy Elliott being exactly what he appeared - a Red HerringSacrificial Lamb. Editorial supposedly got cold feet at the last minute and forbade Loeb and Lee from using Jason. Although someone at DC clearly liked the original idea, but not in this specific context, given that Jason Todd was later revived as the Red Hood for Under The Red Hood.
One Steve Limit: Averted in the casting: the film actually has two people named Peyton List playing different roles (Peyton List reprising her role as Poison Ivy from Gotham, and Disney star Peyton R. List playing Batgirl).
Throw It In!: Harley humming a few notes of "Entry of the Gladiators" wasn't in the script, it was improvised by Hynden Walch. The writer, Ernie Altbacker, noted in the commentary that if he actually wrote out "Dah dah dah dah dah dah dah dah dah dah", he would've looked crazy.
What Could Have Been: In 2016, at the San Diego Comic-Con, Kevin Conroy and Mark Hamill floated the idea that they could act in an Animated Adaptation of Batman: Hush. This movie, obviously, has Jason O'Mara and Jason Spisak instead.