The movie is dedicated to DC Comics artist and writer George Pérez after the ending credits. He died in May 6, 2022.
The comic book "Crisis" starts out including more obscure DC heroes and their correspondent antagonists, rather than DC's mainstream icons. Dawnstar, Firebrand, Psycho Pirate, Killer Frost, Kamandi, Psimon, Geo-Force, Arion, Firestorm, Cyborg and the Earth-2 Superman formed the first team roster recruited by Lyla and the Monitor to fight the title multiversal apocalypse.
In the comic books, Power Ring from the Earth-3's Crime Syndicate was Hal Jordan (renamed as Harold Jordan in this universe). In the movie, Power Ring is John Stewart.
The Spectre's line "Death is better looking" is likely a reference to The Sandman's incarnation of Death and her appearance in DC Showcase: Death (2019).