Trivia

In the behind the scenes featurette, voice director Andrea Romano reveals that James Woods recorded all of his lines as Owlman via satellite from a studio in Connecticut.

Despite a heavy rewrite, Justice League: Crisis on Two Earths still contains some elements that bridge the gap between the series finale of Justice League (2001) and Justice League Unlimited (2004):

• The Justice League has six core members, as it was after Hawkgirl leaving in Starcrossed: Part III (2004)
• The League is assembling new Watchtower following the destruction of the original in Starcrossed: Part II (2004)
• They have also just finished building and testing the teleporter
• Wonder Woman addresses Batman by his real name. The League's secret identities were revealed to each other in "Starcrossed: Part II".
• Wonder Woman keeps Owlman's jet, which gets stuck in "chameleon mode". It is almost identical in appearance to the Invisible Jet she used in "Justice League Unlimited".
• Batman explains to Superman how they are "understaffed." He brings in Aquaman, Black Canary, Red Tornado, Black Lightning and Firestorm to fight Superwoman and company aboard the Watchtower and keeps them around to start expanding the League.
• Flash's character model and facial expressions are very similar, despite the different styles.
• Green Lantern mentions that Flash has a car, which appeared in the second season of Justice League.

The only indications that this is not a bridge between Justice League and Justice League Unlimited are J'onn J'onzz's costume being significantly different, Aquaman sporting his classic orange-and-green costume rather than the look he's had in his two previous appearances, and Green lantern being Hal Jordan, rather than John Stewart.

As Green Lantern/Hal Jordan and Power Ring, Nolan North was the only member of the voice cast to play both a heroic member of the Justice League and his villainous Crime Syndicate counterpart.

Originally titled "Justice League: World's Collide", Dwayne McDuffie's script was commissioned for a planned direct-to-video feature in 2004 meant to bridge the finale of Justice League (2001) and the beginning of Justice League Unlimited (2004). However, due to a tight TV schedule and various other problems, it was not produced then.

When J'onn J'onzz shares his past memories with Rose, the Justice League can be seen fighting Starro the Conqueror. Starro the Conqueror is the first villain the original Justice League of America ever fought in the comics (Brave and the Bold #28, 1960).