Prove It

This guy goes to a grocery store and asks the clerk behind the counter for two cans of dog food.

"Do you have a dog?" asked the clerk.

"Yes I do!" replied the puzzled customer.

"I'm sorry sir," said the clerk, "but you're going to have prove to me that you have a dog before I can sell you dog food."

Back home went the frustrated customer to get his dog and pulled it on its leash all the way back to the store.

"Here's my dog!" wheezed the tired customer.

"Thank you sir, here are your two cans of dog food."

Two days later the guy returns to the same store and goes up to the same clerk and says, "Two cans of cat food please."

"Do you have a cat sir?"

"Of course I do!" said the exasperated customer.

"I'm sorry sir, but I have to see your cat before I can sell you cat food."

The guy storms out of the store, goes home, grabs his cat, drags it back to the store and holds up the cat by its tail for the clerk to see.

"Thank you sir, here are your two cans of cat food."

The very next day, the guy returns to the store, approaches the clerk and places on the counter a white shoebox with a small hole on the cover.

"Yes sir," asked the clerk, "What can I do for you?"

"Put your finger in the hole" ordered the customer.

"I beg your pardon?" said the clerk.

"Do as I say!" ordered the guy.

Cautiously the clerk slid his finger all the way in the hole.

"Pull it out and tell me what it looks like," said the guy.

The disgusted clerk says, "It looks like ..."

To which the customer replied, "THAT'S RIGHT!! Now give me two rolls of toilet paper!"