Following up my post about the final episodes of "Batman: the Animated Series", I found this page with excerpts from the comic book "Mad Love,", which was adapted into one of the best episodes of that last "Batman" season. The comic was written by Paul Dini, who more or less created Harley Quinn and used the longer comic story to explain her origin and her sick relationship with the Joker; the artwork, by series producer Bruce Timm, is a cross between the style of the TV series and the work of Mad's Harvey Kurtzman. The fantasy sequences -- which the TV adaptation didn't have room for -- are very Kurtzmanesque:
Note the in-joke of Buster and Babs Bunny (from "Tiny Toon Adventures," which Dini and Timm and many of the other "Batman" people worked on) hanging from nooses.
The direct-to-video movie Batman Beyond: Return of the Joker hinted at a resolution to the Joker and Harley's relationship; without giving it away, we see that her wacked-out desire for a perfect sitcom-style family finally sort of meshes with the Joker's obsession with finding a way to get Batman's goat. But it didn't really deal with it the issue in any detail, because the sequence was only a ten-minute flashback within a Batman Beyond movie. Good as that movie was, I wish someone would go back and make that sequence into a movie of its own; it just has more resonance than the story of the teen futuristic Batman.