Who said it?

Ah, music. A magic beyond all we do here!

I suppose you think it's funny that Longbottom here heard the story and believed it, too?

I warn you - I'm armed!

My dear boy, you must see how foolish it would be of me to allow you to remain at the castle when term ends.

The story goes that Slytherin had built a hidden chamber in the castle, of which the other founders knew nothing.

When in doubt, go to the library.

Let's do this in pairs, as there are so many of us. I'll go through first with Harry.

Never forget that when thirteen dine together, the first to rise will be the first to die!

Hagrid lost his case. Buckbeak is going to be executed.

Wet.

Obviously.

Doctors? Those Muggle nutters that cut people up?

I think there is something trying to get our of your wardrobe.

Where do you think I would have been all these years, if I had not known how to act?

Patronuses can change, though, can't they?