Much of the voice-over work was done with the actors in the same room in order to let them play off of one another.
Uncommonly enough for a film (especially an animated one) the newspaper article regarding the election of Lex Luthor as president, though only visible for a few seconds, is a full, comprehensive story from start to finish. This includes the details of the campaign, the states where Luthor won, the name of the opponent (Mr. Diaz), Luthor's running mate (Max Yezpitlek) and his aide (Amanda Waller), the reaction of the vice-president and the number of Luthor's administration (46th). The article even closes with a praise to the American electoral system.
Before Superman and Batman face off against the hoard of villains, Batman tells Superman "Your funeral" which Superman responds with "Already had one."
Superman is referring to the "Death of Superman" storyline which was adapted into the first DC Universe movie Superman: Doomsday (2007).
The half Superman half Batman rocket created by Toyman strongly resembles the villian Composite Superman.
Tim Daly, Kevin Conroy, Clancy Brown, and CCH Pounder are no strangers to their roles in this movie. Conroy has done the voice of Batman in every major animated Batman series since 1992 (except for The Batman (2004) and Batman: The Brave and the Bold (2008)) as well as voicing the character in Justice League (2001) and Static Shock (2000). Daly and Brown did the voices of Superman and Lex Luthor in Le avventure di Superman (1996), and Brown also portrayed Luthor in Justice League (2001) and Justice League Unlimited (2004). Pounder had voiced Amanda Waller in Justice League Unlimited (2004).