DOCTOR: Cheer up. Look, there's a mouse.

CHARLEY: I am deeply cheered.

DOCTOR: It's one of the most beautiful things about lady time isn't it? How nothings constant, how everything decays and changes.

CHARLOTTE: You call that wonderful?

DOCTOR: I call it absolutely beautiful. How would it be if everything was always the same? If you never got too big for your dresses? If you never got to pass them onto your sister? If the rainy autumn lasted forever and spring never came? At least I change. I'm stumbling my way through bodies like I own a particularly dangerous bicycle. Grayle never changes, not inside, not who he is. So time piles on top of him and kills everything good. No one should have to go through that.