A Border Patrol agent is on duty. He spots two Mexicans and runs them down. They show him their papers (he thinks they are phony).

He tells them, "O.K. I have a test for you. I want you to use the words 'cheese' and 'liver' in a sentence."

So, the first guy says, "I made a liver and cheese sandwich for lunch."

The agent says, "That was good, you can go. What about you?" he asks the second guy.

He says, "Liver alone. Cheese mine."