Margot

“In fact he was incurably insane and hallucinated more or less continuously, but by a remarkable stroke of lateral thinking his fellow wizards had reasoned that, in that case, the whole business could be sorted out if only they could find a formula that caused him to hallucinate that he was completely sane.*

*This is a very common hallucination, shared by most people.”
― Terry Pratchett, The Truth: Stage Adaptation

“Any fool could be a witch with a runic knife, but it took skill to be one with an apple corer.”
― Terry Pratchett, Carpe Jugulum

“Multiple exclamation marks,' he went on, shaking his head, 'are a sure sign of a diseased mind.”
― Terry Pratchett, Eric

“Double, double, toil and trouble;
Fire burn, and cauldron bubble!”
― William Shakespeare, Macbeth