What old sayings or idioms will produce humorous effects under certain circumstances?

I want to say "look back and smile", which originally means that a beauty's eyes turn and look bright and charming. "Back" means "turn" in the old saying. The meaning of now, er, is well known. Some people say that the wrong usage will become correct if used too much. There are three words in the dictionary: "Now refers to many". Ok, so what we are discussing now is the original meaning of idioms in the old saying.