You don't have to be crazy to live in Gotham, but it helps.
Madness is one of the key motifs in the Batman universe. Two Face, Scarecrow, Poison Ivy: These are all monsters in whom malice has come unhinged from reason; they are lost souls, captured and ridden by some inner demon that, through them, inflicts itself upon the land.
Certainly, if youre looking for a steady supply of baddies, this is one way of insuring youll never run out. I suppose every hero needs a villain whos trying to take over the worldsome cueball with a Napoleon complex. But they cant all aim at the same target. Madness, however, is particular and idiosyncratic, so the storyteller can compose fresh variations before he starts repeating himself.
Then, too, its a way of connecting the villain to his or her schtick. Thats all that a lot of these characters have, right? The Riddler with his puzzles, or Fugate with his timepieces. I mean, who in their right mind would dress up like Tenniels "Mad Hatter" and run through the streets trailing a pair of numbnuts done up like the Walrus and the Carpenter? No one. Hence, Jervis Tetch must be mad.
The Joker is the purest exemplar of the approach. Unlike Tetch or Fugate or Frieze, he has no object of obsession; unlike Isley or Ras al-Ghul, he has no cause; unlike Two Face, he floats free of his own past. He is entirely devoid of reasonin the sense both of rationality and motiveand visits his brand of sadistic jollery upon the world merely because he can.
This simplicity of conception is a source of fertility, but it is also a limitation. Comic books are often melodramatic, but the quick resort to the melodrama of madness can also be sterile. At worst, it reduces the character to a gimmick, but even in the best of hands a clever monomania can become merely monotonous. Everything comes to turn on the ingenuity of plot and execution, rather than the revelation of complicated characters.
I suppose thats why even in a show as resourceful as BTAS, most of the villains run aground after awhile. After his sensational debut in "Mad as a Hatter" and the tour de force of "Perchance to Dream," Tetch wasted away in "The Worry Men" and "Animal Act"; Two Face retreated into the anonymity of the gangster world; and after a magnificent death fight in "Mudslide," Clayface had only glorified cameos. Even the Joker, sustained by a long run of clever stories, gradually became a figure of farce in "Jokers Millions" and "Beware the Creeper." (Though that may also have been a partial function of his TNBA redesign, which left him looking like the Animaniacs evil uncle.) But Arkham has deep dungeons, a fact that does much to disguise just how brief were the arcs of many in the Rogues Gallery.
Still, such brevity does nothing to diminish the Satanic glitter of "Two Face," the wit of "The Clock King," the pathos of "Heart of Ice," or the perversity of "House and Garden"lightning flashes into the darkest corners of the human mind.