Arleen Sorkin (Harley Quinn) played "Amazing Grace" on the kazoo in one take. It was so funny that the crew was laughing during her performance, and immediately after she finished Sorkin and the rest of the voice cast also broke into uncontrollable laughter. Paul Dini said it was fortunate she could do it in one take, as a second would have been impossible to do.
The idea for the episode germinated from a debate between Bruce Timm and Paul Dini, on whether they could do a Batman: The Animated Series (1992) episode without Batman present for the majority of the episode.
In Mark Hamill's introduction for the book "The Joker: A Visual History of The Clown Prince Of Crime" (2011), he specifically mentioned the scene where Joker gave Batman's solemn eulogy, casually sent Sid to his death and then remarked, "Well that was fun! Whos for Chinese?", Hamill credits both the scene and the line, "without Batman, crime has no punchline", with being the single most significant moment to him "getting" the character of the Joker, years later, Hamill would perform the eulogy in Star Wars Celebration VI.
Paul Dini was reportedly worried that Harley Quinn playing "Amazing Grace" on a kazoo might be thought as sacrilegious, but no controversy was raised.
Harley Quinn's real name, Harleen Quinzel, is mentioned for the first time in this episode, but as a pseudonym.