10 Problems With The Joker Nobody Wants To Admit
9. He Is Wildly Inconsistent
Now, part of what makes The Joker such a brilliant nemesis for Batman and such an entertaining character for readers is his unpredictability. The Dark Knight operates (at least partly) on gathering intelligence, knowing his enemy before he actual enters into combat with them, having already prepared for both their strengths and weaknesses. That doesn't really work with The Joker, since every time the two tangle it seems like he's completely reinvented himself.
One week he's a psychopathic mass murderer who will slaughter anybody who gets in his way; the next, he's all about pulling pranks and tricking Batman with one of those guns that shoots out a little flag reading bang!. He's veered between immaculate clown in make up and suit to abattoir owner who wears his own severed face like a crusty mask over his tender flesh.
In Arkham Asylum, Grant Morrison makes the case for The Joker's hypersanity. He realises he's insane, realises he's part of a cycle that sees him constantly being locked up, breaking out, and so on and so forth. It also suggests that the craziness of Gotham is part of what made The Joker so twisted, and each of his personalities is simply a reaction to that. So every morning he wakes up and starts from scratch, because Gotham has a tendency to change overnight (ie according to different writers/artists).
That makes things confusing, though, because sometimes he's a fun-loving rapscallion, and sometimes he's a mass murderer. Where are you meant to stand on him?