PERI: Is it very bad, Doctor?

DOCTOR: It looks like the galaxy’s worst case of athlete’s foot.

PERI: Will you still be my friend, Doctor?

DOCTOR: Hmm?

PERI: Even though I’m turning into a mushroom? I can still grow on you if you let me.

DOCTOR: It’s also making you delirious.

PERI: Are you calling me mental?

DOCTOR: Oh no, I didn’t say that.

PERI: I’m not mental, I’m environmental. Look at my arm. I’m growing my own ecosystem.

DOCTOR: Yes, I can see. You could have your own conservation zone right here.

PERI: Oh, is that good?

DOCTOR: Keep it to yourself. Everyone will want one.

PERI: Maybe I could grow a new arm, huh? Have a little mouse attached to me. Actually, I’d prefer a guinea pig. And while we’re on the subject, Doctor, can’t we have a pet for the TARDIS?

DOCTOR: We’ll discuss it later, Peri.

PERI: Adopt a Dalek, huh? They’ve gotten a bad name, you know. They’re probably really cute underneath all that armour.

DOCTOR: You really are delirious, aren’t you.

PERI: I’m not delirious. I’m American!