The DC character Harley Quinn first appeared in the DC animated universe's Batman: The Animated Series episode "Joker's Favor", in what was initially supposed to be the animated equivalent of a walk-on role. Several police officers were to be taken hostage by someone jumping out of a cake, and it was decided that to have the Joker do so himself would be too bizarre, although he ended up doing it anyway. Thus they created a female sidekick for the Joker; she would become his love interest. Arleen Sorkin, a former star of the soap opera Days of Our Lives, appeared in a dream sequence on that series in which she wore a jester costume; they used this scene as an inspiration for Quinn. Having been friends with Sorkin since college, Paul Dini incorporated aspects of her personality into the character and even got Sorkin herself to voice the character. Quinn was also inspired by a mutual female friend's "stormy but nonviolent relationship," according to Tim.
Mark Hamill attributes the success of Harley Quinn to Arleen Sorkin's performance. "In the script she was just an unnamed Joker "hunch-wench" w/ no discernible personality. When Arleen began reading her lines in that unforgettable voice so poignant & full of heart I nearly fell off my chair! She brought SO much more than was on the page & a legend was born.

---