If you need a bit of library humor, check out IFLANET Library Humour ... if we can't laugh at ourselves, who can?
Here are some examples. Of course, they are categorized.
How many catalogers does it take to screw in a light bulb?
Just one, but they have to wait to see how LC does it first.
Change libraries frequently. It allows you to place the blame on your predecessor for anything that is wrong.