American Girl

The whole thing with the bracelet was really poorly explained (another flaw in Moffat's writing style, really). It WAS the same bracelet as the one Missy was using to control the Cybermen, but the context I picked up was that Danny was sending the kid back from the real afterlife, not the Nethersphere. Clara specifically referred to the Doctor talking about the bracelet being used to cross "dimensional borders" and I'm pretty sure the Gallifreyan Matrix had nothing to do with alternate dimensions and everything to do with simulations. Not to mention if that was a simulation it doesn't explain how the kid got a physical body again. What we have there is, basically, a sci-fi version of an actual afterlife which is now canonical, for better or worse.