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).
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 Walker), 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.
Tim Daly, Kevin Conroy, Clancy Brown, CCH Pounder are no strangers to their roles in this movie. Conroy has done the voice of Batman in every major animated Batman series (except for The Batman and Batman: the Brave and the Bold and The Batman where he did cameo as John Grayson, father of Dick Grayson) as well as voicing the character in both Justice League and Static Shock. Daly and Brown did the voices of Superman and Lex Luther in Superman: The Animated Series, and Brown also portrayed Luther in Justice League. Pounder has voice Amanda Waller in the Justice League animated series and Batman Assult on Arkham
This is one of the few Superman-oriented animated projects connected to producer Bruce Timm and Andrea Romano where Lois Lane made a cameo appearance, but with no lines. This is another break away from the original story, where Lois aided Superman and Batman in distracting Lex Luthor with a televised interview while they made their way towards the White House to confront him. However, it is indicated in the film twice that Lois, at this stage, is aware of his secret identity and are in a relationship.
The trivia items below may give away important plot points.
In the original comic storyline by Jeph Loeb and Ed McGuinness, it was Captain Atom, not Batman, who piloted the Superman-Batman Composite rocket to destroy the kryptonite asteroid. The meteor story was continued in the second arc, as the broken fragments not only fell to earth in multiple versions of kryptonite, but also the ship carrying Superman's cousin, Kara Zor-El (Supergirl). The storyline, also written by Loeb, served to be one of the last projects penciled by the late artist, Michael Turner.