"Only this morning, for instance, I took a wrong turning on the way to the bathroom and found myself in a beautifully proportioned room I have never seen before, containing a really rather magnificent collection of chamber pots. When I went back to investigate more closely, I discovered that the room had vanished. But I must keep an eye out for it. Possibly it is only accessible at five-thirty in the morning. Or it may only appear at the quarter moon- or when the seeker has an exceptionally full bladder."
Do you think there are any earlier references that would've clued us in to something in Book 5?
I think at some point in Book 1, she also mentions that Snape seems to have the horrible ability of reading minds . . .