- The Cast Showoff: Melissa Rauch gets her own musical number as Harley. Rob Paulsen also gets one, which sees him singing a duet with himself, due to playing the twins from Batman: The Animated Series episode "Two-Face".
- The Other Darrin:
- Given that Bruce Timm considers this part of the DCAU, then this counts for Harley Quinn and Poison Ivy, where Arleen Sorkin and Diane Pershing are replaced by Melissa Rauch and Paget Brewster.
- Max and Min, the aforementioned twin lackeys from the "Two-Face" two-parter, also fall under this, as this is the second time Rob Paulsen replaced Micky Dolenz of The Monkees fame in a role.
- In his brief cameo, Booster Gold is voiced by Bruce Timm instead of his voice actor from Justice League, Tom Everett Scott.
- Recycled Script: The movie's plot is pretty similar to the plots of the BTAS-episodes "Harley's Holiday" and "Harlequinade", especially the latter, with Poison Ivy and Jason Woodrue replacing Joker.
- Relationship Voice Actor: Harley Quinn, Jason Woodrow, Sarge Steel, Rhino, Bobby Liebowitz, and the project supervisor are Tizzy, King Kamea, Hale, Sir Finnegan, King Henley, and Calliope.
- Role Reprise:
- Loren Lester as Nightwing, returning to this role since the end of The New Batman Adventures era, having last played the role in the 2003 video game Batman: Rise of Sin Tzu. Kevin Conroy once again playing Batman is a very lesser example since that man is everywhere.
- In the French dub, Kelvine Dumour as Harley Quinn from the DC Animated Universenote , Mathias Kozlowski as Nightwing from Teen Titans, Emmanuel Jacomy as Batman from Justice League vs. Teen Titansnote , Dominique Vallée as Poison Ivy from Justice League: Gotham City Breakoutnote and Saïd Amadis as Swamp Thing from Justice League Darknote .
- Sequel Gap: Batman and Harley Quinn is the first new entry in the DC Animated Universe since Justice League Unlimited ended eleven years prior in 2006. And the first DTV film in that series based on Batman since Batman: Mystery of the Batwoman released in 2003, fourteen years prior.
Trivia / Batman and Harley Quinn