I remember a particularly nice lesson in my high school physics class whereby the teacher introduced us to the idea of statistical mechanics by saying that there's a probability, which we could calculate if we wanted to, of this chair here to suddenly levitate, make a summersault, and then gently land back. He then proceeded by saying that this probability is so astronomically small that nothing of this sort would in practice happen before the heat death of the universe. But it is non-zero.