- Acting for Two: The English dub has a few cases of this:
- All-Star Cast:
- The Japanese dub cast is absolutely insane. There's Kōichi Yamadera as Batman, Wataru Takagi as The Joker, Ai Kakuma as Catwoman, Rie Kugimiya as Harley Quinn, Junichi Suwabe as Deathstroke, Takehito Koyasu as Gorilla Grodd, Yuichi Nagashima (Cho) as The Penguin, Atsuko Tanaka as Poison Ivy, Kenta Miyake as Bane, Yuki Kaji as Robin, Kengo Kawanishi as Red Robin, Daisuke Ono as Nightwing, Akira Ishida as Red Hood, and Hochu Otsuka as Alfred Pennyworth.
- The English dub is also worth mentioning. We have Roger Craig Smith as Batman, Tony Hale as The Joker, Grey DeLisle Griffin as Catwoman, Tara Strong as Harley and Ivy, Adam Croasdell as Alfred and Nightwing, Fred Tatasciore as Gorilla Grodd and Deathstroke, Yuri Lowenthal as Robin and Red Hood, Will Friedle as Red Robin, Eric Bauza as Two Face, and Tom Kenny as Penguin.
- Cowboy BeBop at His Computer: The description in the first English trailer mentions that Will Friedle voices Red Robin and Red Hood, when in actuality, Yuri Lowenthal voices the latter.
- International Coproduction:
- The film is a Japanese-American co-production.
- Interestingly enough, the Latin American Spanish dub is this as well, albeit with a twist: Most of the dub is done in Venezuela just as previous animated works involving either Batman or the DC Universe Animated Original Movies, but Joker's voice acting is done in Mexico, since his previous Venezuelan voice actor, Rubén Leon, decided to quit voicing him due to Warner Bros. refusing to give him a pay raise, and no Venezuelan voice actor wanted to voice him in his place out for respect for his work. With no other option available, Warner decided to give his role to a Mexican voice actor, Javier Rivero, who did Joker's voice from there.
- The Other Darrin: Played straight and subverted in the Japanese version. Kōichi Yamadera and Takehito Koyasu both return from The LEGO Batman Movie, with Yamadera reprising his role as Bruce/Batman but Koyasu who played Joker in that movie instead plays Gorilla Grodd in Ninja. Instead Wataru Takagi takes over as Joker.
- Playing Against Type: Tony Hale, who usually tends to play neurotic characters, voices the hammy, psychotic Joker in this film.
- Relationship Voice Actor: Put it this way: Batman and Catwoman, along with Hol Horse, Jotaro Kujo, Koichi, Terunosuke Miyamoto, Vinegar Doppio and Speedwagon's Ninja Clan, faces against Okuyasu Nijimura, Yoshikage Kira, Anne, DIO, Abbachio, Lisa Lisa, Wilson Phillips and Muhammad Avdol. Yeah, this movie really is a Jojofest.
- Role Reprise:
- The Japanese version gives a very interesting version: Kōichi Yamadera reprises his role as Batman from not only from the dubs of The LEGO Movie and The LEGO Batman Movie, but also from the Japanese dub of the very first Batman film shown in TV Asahi in the 90s.
- Wataru Takagi reprises his role as Pipimi (dressed as Joker) in the above-mentioned Pop Team Epic promo.
- For the English version, Roger Craig Smith, Tara Strong, and Grey Delisle reprise their Arkhamverse roles as Batman, Harley Quinn, and Catwoman, respectively. Tom Kenny also returns to the role of Penguin from The Batman. Fred Tatasciore also reprises his Young Justice role as Deathstroke and Strong also reprises her LEGO Batman 3: Beyond Gotham role as Poison Ivy.
- For the Brazilian dub, Eduardo Ribeiro reprised his role as Batman from The Batman, Batman: The Brave and the Bold and many other animated films. Sergio Cantú reprises his role as Nightwing from Young Justice. Márcio Simões and Hélio Ribeiro reprise their respective roles of Joker and Two-Face from The Dark Knight. José Santa Cruz reprises his role as the Penguin from Batman Returns. Miriam Ficher reprises her role as Poison Ivy from Batman & Robin. Iara Riça, once again, voices Harley Quinn, as in Batman: The Animated Series and most of the subsequent appearances of the character, including the movie Suicide Squad (2016).
Trivia / Batman Ninja