"Fool!" cried the hunchback. "You fell victim to one of the classic blunders. The most famous is 'Never get involved in a land war in Asia,' but only slightly less well known is this: 'Never go in against a Sicilian when death is on the line.'"
I cannot find my copy of the book, or it would have been one of the historical parentheses like:
"This was after stew, but everything is after stew. When the first man crawled up onto land from the ocean, what he had for dinner that night was stew."
If you've never read the book, you've only gotten about half the jokes.