DOCTOR: You, Sir, are a NITWIT!

DOCTOR: I’d like to see a butterfly fit into a chrysalis case after it spreads its wings. Life depends on change, and renewal.

DOCTOR: The least important things, sometimes, my dear boy, lead to the greatest discoveries.

DOCTOR: You know, I am so constantly outwitting the opposition, I tend to forget the delights and satisfaction of the arts, the gentle art of fisticuffs.

DOCTOR: One day, I shall come back — yes, I shall come back. Until then, there must be no regrets, no tears, no anxieties. Just go forward in all your beliefs, and prove to me that I am not mistaken in mine. Goodbye, Susan, goodbye, my dear.

DOCTOR: But you can't rewrite history! Not one line!