First Doctor: There is good and there is evil. I left Gallifrey to answer a question of my own. By any analysis, evil should always win. Good is not a practical survival strategy - it requires loyalty, self-sacrifice and love. So, why does good prevail? What keeps the balance between good and evil in this appalling universe? Is there some kind of logic? Some mysterious force?
Bill Potts: Perhaps there's just some bloke, wandering around, putting everything right when it goes wrong?
Bill Potts (to 12th): You're an arse. Do you know that? You're a... You're a stupid bloody arse.
First Doctor: If I hear any more language like that from you, young lady, you're in for a jolly good smacked bottom.
Twelfth Doctor: Can we just pretend that that never happened?
Bill Potts: I'm a broad-minded girl - I mean, I know we have this whole professor/student thing going on...
Twelfth Doctor: Can we never, ever talk about this again?
Bill Potts: I hope we talk about it loads. I hope we spend years laughing about it.