A man went into a grocery store, got 3 cans of dog food, and walked up to the checkout counter.
The cashier asks the man, "Sir, do you own a dog?"
The man replies, "Yes I do."
The cashier then asks, "Do you have the dog with you?"
The man replies, "No, I left it at home."
The cashier then says, "I'm sorry, but I can't sell you this dog food unless I see your dog."
A few days later the man walks into the same store, gets 3 cans of cat food, and walks up to the checkout counter.
The same cashier asks, "Sir, do you own a cat?"
The man replies, "Yes I do."
The cashier then asks, "Do you have your cat with you?"
And the man replies, "No, I left it at home."
Then the cashier says, "I'm sorry, but I can't sell you this cat food unless I see your cat."
A few days later the man walks into the store, this time carrying a paper bag.
He walks up to the same cashier, and asks him to put his hand into the bag.
The cashier says, "It feels warm, soft, and gooey."
The man then says, "Now, can I go back and get 3 rolls of toilet paper?"