One way to enumerate them would be, as CCC has just pointed out, with integers where irrationality denotes acausal worlds and rationality denotes causal worlds.

This however doesn't leaves space for Stranger Things;

Well, I admit that I had originally considered that Stranger Things would most likely be either causal or acausal; I can't really imagine anything that's neither, given that the words are direct opposites.

In the case of a Stranger Thing that's strange enough that I can't imagine it, we could always fall back on the non-real complex numbers, which are neither rational nor irrational (and are numerous enough to make real numbers look trivial by comparison).