A guy is driving around the back woods of Tennessee and he sees a sign in front of an old shanty-style house: "Talking Dog For Sale." He knocks and the owner appears and tells him the dog is in the backyard. The guy goes into the backyard and sees a nice looking Labrador Retriever sitting there.
"You talk?" he asks. "Yep," the dog replies.
After the guy recovers from the shock of hearing a dog talk, he says "So, what's your story?"
The dog looks up and says, "Well, I discovered that I could talk when I was pretty young. I signed up for a job at the airport to do some undercover security, wandering near suspicious characters and listening in. I uncovered some incredible dealings and was awarded several medals. I wanted to help America, so I interviewed with the the CIA. In no time at all they had me traveling around the world and hanging out with spies and world leaders. After all, no one figured a dog could eavesdrop. I proved to be one of their most valuable spies for a decade. But the jetting around really tired me out, and I knew I wasn't getting any younger. So, I decided to settle down. I got married and had a mess of puppies. Now I'm just retired."
The guy is amazed. He goes back in and asks the owner what he wants for the dog.
"Ten bucks," the guy says.
"This dog is amazing! Why on earth are you selling him for just ten dollars?"
"Because he's a liar! He never did any of that stuff!"