Martha: You step on a butterfly, you change the human race.
The Doctor: Then don't step on any butterflies. What do you have against butterflies?

The Doctor: Elizabethan England, not so different from your time. They've got recycling, water cooler moment... global warming.

The Doctor: Go home, you can tell everyone you met Shakespeare.
Martha: Then I could get sectioned.

Martha: And those are men dressed as women, yeah?
The Doctor: London never changes.

The Doctor: I'm Sir Doctor of Tardis and this is my companion Martha Jones.
Shakespeare: Interesting, that bit of paper. It's blank.
The Doctor: Oh, that’s very clever. That proves it.

Martha: And why are you telling them that?
The Doctor: ...Dark Ages. If I tell them the truth they'll panic and think it's witchcraft.
Martha: Well what is it then?
The Doctor: Witchcraft.

Shakespeare: And you, Sir Doctor. How can a man so young have eyes so old?
The Doctor: I do a lot of reading.

Shakespeare: And you Doctor. I might learn more about this constant performance of yours.
The Doctor: All the world's a stage.
Shakespeare: Hm. I might use that.

Martha: So magic and stuff. That's a surprise. It's all a bit Harry Potter.
The Doctor: Wait until you read book seven. Woah. I cried.

The Doctor: Rage rage against the dying of the light.
Shakespeare: I might use that.
The Doctor: You can't. It's someone else's.

Martha: Woah, nelly! I know for a fact you have wife in country.
Shakespeare: But Martha, this is town.

Love’s Labors Won. The sequel is never as good as the original.

Martha: Let us out! Let us out!
The Doctor: That's not going to work. The whole building's shouting that.

Martha: What did you do?
The Doctor: I named her. The power of a name. That's old magick.
Martha: But there's no such thing as magic.
The Doctor: Well,... there's a science to it...

The Doctor: The play's the thing! And yes, you can have that.

The Doctor: Oh, how to explain the machanics of temporal time flux. I know! Back to the Future.
Martha: The movie, Back to the Future?
The Doctor: No, the novelization of the movie.

As for you, Sir Doctor. Fascinating. There is no name. Why would a man hide his title in such despair?

The old ways of blood and magick.
Hm. Busy schedule.

The Doctor: Well that's just cheating.

The Doctor: You might call that magic. I call it a DNA replication module.

The Doctor: Expelliarmus! Good 'ol J.K.!