Originally Posted by electriclite
Or they incorporate a character that never existed in the comics: Harley Quinn
The history of comics is tantamount to this conversation, between editor and writer:
writer: so, I have this really cool idea for a new character, its [insert unusual angle here] and [he/she] teams with [insert established character here] and does [insert crazy shit here] and in the end [insert resolution that only makes plot more complex here]
editor: wow, really? Well, okay, you're [insert name of famous creator who has free reigns because the company owes them, big time, here] so, I guess we go with it.
Harlequinn was a perfect example (even though it was TV), DC had tried, for ages, to give the Joker a sidekick, and eventually, after decades of frustration, it was decided it just couldn't be done. Nobody told Paul Dini. The thing is, a sidekick to the Joker has to be an interesting character in their own right, while, at the same time, not upstagging Mr. J (you know what happens when Mr. J gets upstaged, he gets very killy) The beauty of the Harle-Joker dynamic is that they are both completely insane, but insane in very different ways that play off of each other. Same thing with the Harle-Poison Ivy relationship, and Harle-Catwoman, reading Gotham Sirens is a hoot (the harle-catwoman-ivy team-up book) because Ivy is crazy, she perfers plants to people, and she's a maniacal eco-terrorists who seduces men with plant based toxins. Catwoman is a Kleptomaniac, she steals everything that isn't nailed down, and some stuff that is. But, compared to Harle, Ivy and Catwoman are the the "straight" man.