Hey there--open up! Something outrageously zany is knock-knocking at your door, ready to tickle your funnybone. Knock-knock. Who's there? Boo. Boo who? Well, you don't have to cry about it. Or, how about this one: Knock-knock. Who's there? Flea. Flea who? Flea blind mice. You won't want to keep these "yuks" to yourself!