When Batman is shot while pursuing Two Face, he is hit in the chest. In the book this reveals a section of armor beneath the bat symbol and, speaking to himself, he says this is why he has a bright yellow target on his chest - to give snipers something to aim at instead of more vulnerable places.
The red phone that the Commissioner uses to contact Batman has the same design and beeping tone that the one from the 1960s TV series had.
In the early 2000s, the Hughes brothers were offered the chance to direct a live-action adaptation of "The Dark Knight Returns," but the project never materialized. They wanted Clint Eastwood to play Bruce Wayne/Batman. Eastwood would've then been in his early 70s, whereas in the comic book Batman is 55.
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."
The scene where Batman pulls the Mutant through the wall is similar, if not, identical to the scene where RoboCop pulls the gunman through the wall in RoboCop (1987), both are played by Peter Weller. Frank Miller also wrote for both Robocop and Dark Knight.