The joker in the batman universe does have a superpower. No one could pull off half the random things Joker does unassisted, all the near deaths, convoluted plots and inevitable escape attempts, impossible without some other force at work. But really, it’s his name that gives it away. He has got a power any comedian, class clown or joker would kill for.
He has a supernaturally good sense of timing.
That’s why all his schemes can work and why the only times he gets caught are when he can safely get away later. Because even if he’s unaware that he’s doing it, he’s always in the right place at the right time. Joker probably isn’t aware he even has this power, but its part of the reason he never gets over his insanity. Because everything always works out for him, he’s never confronted with facing reality aside from the chaos he creates.