Yeah, the alternates-in-every-world is sort of on the level of, "The dinosaurs never went extinct. The year is 1967, and Richard Nixon is facing off against a velociraptor opponent in the Republican primaries . . ." As you see, I am capable of constructing quite elaborate fan theories, but for that one I just put my hands over my ears and go, "It's magic, it's magic, it's magic . . ."

I think it is canon that all the Series except Eleven are in fact Series. And that Julia and Roger are only witches and not enchanters.

There's a sort of allusion in Lives of Christopher Chant to people with somewhere between one and nine lives, I think? But it's never picked up again.