MAN: I'd like to buy some dog food.

CHECKOUT LADY: Do you have a dog?

MAN: Yes.

CHECKOUT LADY: Where is he?

MAN: He's at home.

CHECKOUT LADY: I'm sorry, I can't sell this dog food to you unless I see the dog. Store policy.

The next day, the man returns.

MAN: I'd like to buy some cat food.

CHECKOUT LADY: Do you have a cat?

MAN: Yes.

CHECKOUT LADY: Well...where is he?

MAN: He's at home!

CHECKOUT LADY: Sorry, I can't sell this cat food to you unless I see your cat.

The next day the man returns.

CHECKOUT LADY: What's in the sack?

MAN: Put your hand inside.

CHECKOUT LADY: Hmmm...It's warm and moist! What is it?

MAN: I would like to buy some toilet paper.