You know, it occurred to me, I'm still not sure what the deal was with making "Wild Blue Yonder" (the song) the through-line of the episode. Was it with the edge of the universe being like the endless sky? Is it the TARDIS being blue, though it's a stretch to call it a "yonder." What about the debate over whether it was a fun, jaunty song or a martial one, that didn't seem to go anywhere, either. That last part, at least, feels like RTD's old habit of raising probing, uncomfortable questions, and then just dropping them without exploring or answering them.