A pair of money quotes from Sir Terry Pratchett‘s take on Dr. Who:
I saw the occasional episode in which, generally speaking, the world was attacked by teapots.
and
It’s a law – well at least a guideline – in writing plays that if somebody is going to be killed with an axe in the third act, then the axe should be visible hanging on the wall in the first act, and, for the hard of thinking, should be the subject of a line of dialogue that would go something like “you shouldn’t leave that around, it could do someone a mischief.”