So our car had to be fixed yesterday - turned out it cost over $600 for a sensor or something. I was thinking last night it would be funny to, throughout your day, make up expressions that don't make any sense. Like when the guy showed me the bill, I could have said "Wow, that chihuahua won't bark!"
Sara's idea, "You don't have to tell me a toilet seat's round!"
Or "The moon won't be split in half, that's for sure"
Just make them up like this and people could spend half the day trying to figure out what you were talking about.