Never knowingly be serious. Rule 27.

“Angel Bob: Doctor? Excuse me, hello, Doctor? Angel Bob here, sir. The Doctor: A…”

“The Doctor: I've seen bigger.Clara: Really?The Doctor: Are you joking? It's mas…”

“Amy Pond: 'I thought... well, I started to think you were just a madman with a …”

“Well we've moved through the funfair a bit - we've done the rollercoaster, now …”