On the lines of Foolestroupes quips:-

What does an occasional table do when it isn't.
Why is there only one Monopolies Commission.
When the person inventing the drawing board got it wrong...what did they go back to?
Why is there only one word for Thesaurus?
Why do so few people know how to spell Dyslexia?
If cabbage is good for you...why do cabbage white butterflies only live for one day?
Why does someone always answer the phone when you get a wrong number?