I was thinking, initially, that the 'player characters' where just previously entangled systems. Anytime anything that has previously decohered interacts with a system still in quantum superposition a new 'player character' would be created.
But that seems like an exponential process so it immediately makes me ask: Why isn't everything entangled at this point? Is there that much in the universe still in superposition that it just hasn't happened or can something that has previously been entangled become un-entagled and re-enter a state of superposition?
If you want to twist your mind over this subject, read Quantum Enigma by Bruce Rosenblum and Fred Kuttner[1]. It's written by a couple of quantum physics researchers who spend some time thinking about WTF quantum reality means. It's one of the few metaphysical books on quantum physics I've found that sticks to the real science (and, as a result, has no conclusions).
The new 'player character' on decoherence is, essentially, the many worlds interpretation. That is a valid interpretation, and while it matches the data (and may not be falsifiable), I have a hard time buying it (where does all that energy come from??).
But that seems like an exponential process so it immediately makes me ask: Why isn't everything entangled at this point? Is there that much in the universe still in superposition that it just hasn't happened or can something that has previously been entangled become un-entagled and re-enter a state of superposition?