The Joker is a supervillain appearing in American comic books published by DC Comics. Created by Bill Finger, Bob Kane, and Jerry Robinson, the character first appeared in the debut issue of the comic book Batman on April 25, 1940. Credit for the Joker's creation is disputed; Kane and Robinson claimed responsibility for his design while acknowledging Finger's writing contribution. Although the Joker was planned to be killed off during his initial appearance, he was spared by editorial intervention, allowing the character to endure as the archenemy of the superhero Batman.

Barbara Gordon is a superheroine appearing in American comic books published by DC Comics, commonly in association with the superhero Batman. The character was created by television producer William Dozier, editor Julius Schwartz, writer Gardner Fox, and artist Carmine Infantino. Dozier, the producer of the 1960s Batman television series, requested Schwartz to call for a new female counterpart to the superhero Batman that could be introduced into publication and the third season of the show simultaneously. The character subsequently made her first comic-book appearance as Batgirl in Detective Comics #359, titled "The Million Dollar Debut of Batgirl!" in January 1967, by Fox and Infantino, allowing her to be introduced into the television series, portrayed by actress Yvonne Craig, in the season 3 premiere "Enter Batgirl, Exit Penguin", in September that same year.