- Casting Gag:
- Kal-El is voiced by Sam Daly, whose father is best known for being the voice of Superman.
- C. Thomas Howell as Professor Zoom and Danny Huston as Sam Lane could count as this. Replace the Flash and Superman as the targets of Zoom and Lane's respective torments with Aaron Hotchner and Wolverine and you've got basically, respectively, George Foyet and William Stryker.
- Yo-Yo, an Expy of Harley Quinn, is voiced by Hynden Walch, who also voiced Harley in The Batman. The French dub did something similar by having Yo-Yo be voiced by Kelvine Dumour, the voice of Harley in Batman: The Animated Series.
- In the French dub, Batman/Thomas Wayne is voiced by Saïd Amadis, who also voiced Batman/Bruce Wayne in Batman: The Dark Knight Returns.
- Executive Meddling: The film being used as a starting point for the DC Animated Movie Universe was an edict given to James Tucker late during production to this, hence the stinger to set up Justice League: War.
- Fake American: Scottish Kevin McKidd as Thomas Wayne, complete with the trademark gravelly Batman voice. Also Canadian-born Nathan Fillion as Green Lantern.
- Role Reprise:
- Bruce Wayne and Lois Lane have their voice actors from the DC Animated Universe (Kevin Conroy and Dana Delany, respectively). Wonder Woman is voiced by her voice actress in Justice League: Crisis on Two Earths, Deathstroke by his voice actor on Teen Titans, and Hal Jordan by his voice actor on Green Lantern: Emerald Knights and Justice League: Doom. Additionally, Etrigan and the President are voiced by Dee Bradley Baker and Kevin Michael Richardson, as in Batman: The Brave and the Bold
- In the French dub, several voice actors from previous adaptations reprised their roles here:
- From the DC Animated Universe: Emmanuel Jacomy as Superman/Clark Kent and Véronique Augereau as Lois Lane.
- From The Batman: Christophe Lemoine as the Flash/Barry Allen and Adrien Antoine as Batman/Bruce Wayne.
- From Superman/Batman: Apocalypse: In addition to Batman and Superman, Delphine Braillon as Wonder Woman/Diana Prince.
- From Green Lantern: First Flight: Paul Borne as Green Lantern/Hal Jordan.
- From Batman: The Brave and the Bold: In addition to Flash, Batman, Superman, Lois, and Wonder Woman, Michel Vigné as Aquaman, Jérôme Pauwels as the Flashpoint version of Captain Marvelnote , Marc Perez as Orm, and Jean-Claude Donda as Captain Boomerang.
- From Justice League: Doom: In addition to Flash, Batman, Superman, Lois, Wonder Woman, and Green Lantern, Jérôme Pauwels as Cyborg.
- From Young Justice: In addition to Flash, Batman, Superman, Wonder Woman, Aquaman, and Captain Marvel, Paul Borne as Lex Luthor, Jean-Claude Donda as Deathstroke, and Michel Vigné as Captain Atom.
Trivia / Justice League: The Flashpoint Paradox