Joker World

Joker worlds are the utterly out-of-sequence strange planets to be found at seemingly random intervals in the chain of Long Earths. they are characterised by the tantalising hint that some sort of external shaping and interference has been performed here by an intelligent outside force. And where Stepping between worlds betrays a gradual subtle pattern of change as Earths progress, like the flickering of a film, the jokers stand completely outside this harmonious pattern.

it is discovered in Book:The Long Cosmos that there is, in fact, a pattern to their distribution.