Countless worlds, people, epochs, and possibilities. There are few outright laws governing the behaviour of unstable concepts like the Multiverse, but there are some rules of thumb that have been proven correct more often than not. One of these is that the only thing we know is going to happen, is that we don't know what's going to happen. The Joker represents the infinite possibilities of the Multiverse, and how much luck governs our experiences within it.