"Must you bring people back?"

"Yes," said the Hat, shortly.

"They will probably touch things. Hogwarts has a very delicate ecosystem, you know. If they go trying to eradicate one species, they are going to throw the whole thing off balance! Or if they go rebuilding some of those walls or removing the cave ins, they'll change the migration paths and then who knows what will move to where when the time comes. It took me years to figure out this much! Oh, and if they start getting into the new or the old passages..."

"...yes," added the Hat, not disareeing vastly at this point.

"On the other hand, it could be interesting to see how a new organism reacts in the system. I just hope they don't get all murder-y like humans tend to do."

"Yes," said the Hat, "well, you know how most humans get. They don't quite know how to handle things they don't understand, and a certain amount of murder-y human behaviour has started, though so far they've only murdered the monsters that would have eaten them. Mostly. Of course, if they had someone to intervene, someone who looked more or less, that may work wonders..."

"Say, Sir Sorting Hat, I don't believe you sorted me the last time we spoke. Will you permit me to remain here? Not that you can kick me out. Although it might be fun to see what tricks you have to try and do it."

The Hat grinned too, into her head. Could they feel him making expressions? He was never all that sure. "I'm not in charge of the Housing around here, and I firmly refuse to be. Haven't I got enough on my plate? But," he added, seriously, "your assessment of where you would land up is not entirely inaccurate, as far as I'm concerned."