Harley Quinn

Dr. Harleen Frances Quinzel, also known as Harley Quinn (a pun on the word "harlequin"), first appeared in the Batman: The Animated Series episode "Joker's Favor", where she served as a humorous female sidekick to the Joker. In her first appearances she was depicted as a character completely devoted to the Joker, totally oblivious to his psychotic nature and obvious lack of affection for her; this characterization has remained more or less consistent throughout her subsequent appearances.

The origin of the character was recounted in a 1994 graphic novel The Batman Adventures: Mad Love. Told in the style and continuity of Batman: The Animated Series and written and drawn by Paul Dini and Bruce Timm (two of the producers of the animated series and Harley's creators), the comic book reveals Harley's origins as an Arkham Asylum psychiatrist who falls in love with the Joker. The story was widely praised and won the Eisner and Harvey Awards for Best Single Issue Comic of the Year.

The Mad Love story was originally thought too violent for the animated series, but was eventually used in The New Batman Adventures episode "Mad Love" in 1999. This made it the first "animation-style" comic book to be adapted for the series, a practice that would be continued for the episode "Holiday Knights".