Lex Luthor's bodyguard's Mercy Graves was first introduced in Superman: The Animated Series, and came to be considered analogous to Harley Quinn given this transition from animation to comics. In 'World's Finest' aka "The Superman/Batman Movie", the two serve as rivals to each other, culminating in a ferocious catfight while Joker and Luthor civilly discuss business. A Mercy/Harley fight was redone during the "Superman: 'Til Death Do Us Part" storyline, in which Joker and Quinn came to Metropolis to harrass Lex Luthor.
While Harley's outfit is similar to Mercy's, it actually is based on Harley's first appearence in the Batman: The Animated Series episode "Joker's Favor," (which preceded Mercy's first appearance) where she dresses up as a chauffeur to pick up Charlie Collins, who had been blackmailed into helping the Joker.
