After reading a review a few days ago of a new issue of a Batman comic involving a battle between the Dark Knight and the Batman Who Laughs, I decided to read a collection containing an introduction to the character. Basically the idea behind the Batman Who Laughs is a Batman-Joker mashup created when an alternate-universe Batman is infected with a Joker toxin that rewrote his morals while retaining his ability for strategic thinking. The result instant supervillain.
An evidently it's a popular one, too. What a started out as one of a number of new "Nightmare Batmen" created for an "event" storyline has evidently become a new fan favorite. And while I can see why, it strikes me as a concept that can get old pretty damn quickly. Because, like the Maestro Hulk and the Maker version of Reed Richards in Marvel comics, while creating a powerful evil doppelganger makes for an interesting one-off, it wouldn't take too many defeats for the Batman Who Laughs to become another sad part of the "rogue's gallery."