In the scene where Commissioner James Gordon is picking up nicotine gum in the convenience store before killing the Mutant gang member, there are other DC Comics titles on the magazine rack. Ones featured notably are Swamp Thing (1982), Watchmen (2009), V for Vendetta (2005), and Sandman. All but "Sandman" have received a movie treatment.
For children's marketing reasons, the scene where Commissioner Gordon is smoking a cigar in the graphic novel is replaced with nicotine gum. Commissioner Gordon actually explains this, stating, "My wife made me quit the cigars."
Although Frank Miller's graphic novel "The Dark Knight Returns" was originally adapted into two parts, Warner Home Video re-edited them into a single direct-to-video animated feature, "Batman: The Dark Knight Returns - Deluxe Edition."
This movie stars Peter Weller as Bruce Wayne/Batman, who was the title character in RoboCop 2 (1990), which Frank Miller scripted. Miller is responsible for the graphic novel that this animated film is based upon. During the rooftop scene where Batman is taking out Two-Face's henchmen, two of his thugs resemble the gang members from the original Robocop (1987) movie, who murdered Weller's character.
This was not the first time Wade Williams had done a role for projects relating to DC Comics. There are subtle references to Jason Todd returning as The Red Hood in Batman: Under the Red Hood (2010), where Williams portrays Black Mask in that film. He had voiced Mantis/Supreme Chairman in an episode of Batman: The Brave and the Bold (2008), titled "Cry Freedom Fighters!" and Deegan in Green Lantern: Emerald Knights (2011). Most recently, he played the Warden at Blackgate Prison when Selena Kyle was being jailed in The Dark Knight Rises (2012); this was most likely owing to the fact that he played Brad Bellick in Prison Break (2005). Here, he voiced seemingly reformed criminal Harvey Dent/Two-Face in a reversal of roles to both his parts in The Dark Knight Rises (2012) and Prison Break (2005).