Linguistic humor, Funny signs found on real businesses

Morphology

The Electric Company: We would be delighted if you send in your bill. However, if you don't, you will be.

Lexicon and idioms

Sign on an electrician's truck: Let us remove your shorts.

Maternity Clothes Shop: We are open on labor day.

Car Dealership: The best way to get back on your feet—miss a car payment.

Bowling Alley: Please be quiet. We need to hear a pin drop.

Syntax

Cafeteria: Shoes are required to eat in the cafeteria. Socks can eat any place they want.