Warnings of Three...

 Don't eat black box. Especially with your lobster claw.

Gotcha.

 Black box will hypnotize you, causing you to die. This is bad.

Gotcha.

Wha?

Proof!

 

When the Greys come to Earth and try to blend in, this is how you'll spot them. They wear tacky visors and can't pump gas. When they finally figure out how to pump gas, all you'll have to go on is the visor.

well, duh

The most ridiculous thing about this sign is where I found it: