Nothing can ever be a rule in drama, because then you're saying certain things won't ever happen, and that would be very boring.
Steven MoffatMadame Kovarian: The anger of a good man is not a problem. Good men have too many rules. The Doctor: Good men don't need rules. Today is not the day to find out why I have so many.
Steven MoffatThe difference between a beautifully made failure and a beautifully made hit is who you've got playing the leads.
Steven MoffatThink you've seen it all? Think again. Outside those doors, we might see anything. We could find new worlds, terrifying monsters, impossible things. And if you come with me... nothing will ever be the same again!
Steven Moffat