So, the aunt. Where is she? "Out." Not a problem, apparently. The Doctor -- in case we didn't notice -- is amazed by her unflappability: "Box falls out of the sky, man falls out of box, man eats fish custard, and look at you, just sitting there. So you know what I think? Must be a hell of a scary crack in your wall."
I like that he's making friends with Amelia at this age -- even though the consequences are disastrous -- because that makes their whole relationship different. It's not precisely like the Reinette/Slow Path Thing, because she had this full life and because she really was in love with him: It's an Imaginary Friend Thing, which is much cooler and makes the eventual weirdness and anger of Amy a lot more fun. I guess I can see the parallels, but when you're dealing with a show entirely about a time-traveler and his relationships to mortals, it seems like this would happen a lot more.
They tromp upstairs, and he quotes himself: "You've had some cowboys in here..." Quickly explains that he doesn't mean actual cowboys, "though that can happen," and Amelia produces a smiling apple from her pocket, handing it over: "I used to hate apples, so my mum put faces on them." He agrees that Amelia's mum sounds awesome, and it is a very Doctor thing to do, and he pops it in his own pocket. It would have made sense to do this in the original conversation about apples, but whatever. So he explains that the crack is a Crack, like, it's a crack in everything and even if you knocked down the wall it would still be there. Which is what I was hoping it was, so that's cool. Also cool: Foreshadowing.
"Everywhere, in everything. It's a split in the skin of the world. Two parts of space and time that should never have touched, pressed together."
I do think that last sentence will bite us in the ass, around twelve episodes from now. Just as the Doctor intuits that there are probably voices coming out of that crack sometimes -- and empties a glass of water with one of the cutest gestures I've ever seen a grown man pull, to listen -- a voice comes out of the crack: "Prisoner Zero has escaped!" Amelia's heard about this before, from the crack; the Doctor explains helpfully that there's a prison on the other side of the crack, and somebody's gotten out. "Do you know what that means? You need a better wall." Word. But then he goes all Doctor and says that the only way to close the breach is to "open it all the way." Very Doctor: "The forces will invert, and it'll snap itself shut." Or another thing, which he doesn't say, but is a very bad thing: