Batman: The Animated Series Joker, Harley Quinn and Batman Publicity Cel with Key Master Background (Warner Brothers, 1992)

A unique and momentous piece of animation that showcases the first time the world saw Harley Quinn.
Thirty years ago, this hand-painted, original publicity cel, created to promote the then upcoming Batman: The Animated Series, was first seen on the cover of the August 30 New York Times Television Supplement.
In a lawless scene, Harley (with her infamous pop-gun), and the Joker (with his iconic flag-gun), fight off The Dark Knight Detective. This cel predates the Princess of Crime's first appearance in the comic The Batman Adventures #12 by one year, and was published just a few months before her first appearance in the Batman: The Animated Series episode "Joker's Favor", making this published piece the first time the world would see Harleen Quinzel.
As another first, this image was used in Comics Scene #31 for an article about Batman: The Animated series, which marked Harley's first appearance in a comic, albeit a preview. And in the black and white image, Harley was not named. This cel art also marked the first appearances of Batman and Joker into the now acclaimed DC Animated Universe.