A guy is driving around the back woods of Montana and he sees a sign in front of a broken down shanty-style house: 'Talking Dog For Sale.' He's intrigues, and so he stops and rings the bell. 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 Lab replies.

After the guy recovers from the shock of hearing a dog talk, he says, "So, what's your story?"

The Lab looks up and says, "Well, I discovered that I could talk when I was pretty young. I wanted to help the government, so I told the CIA.

In no time at all they had me jetting from country to country, sitting in rooms with spies and world leaders, because no one figured a dog would be eaves dropping."

"I was one of their most valuable spies for eight years running...
But the jetting around really tired me out, and I knew I wasn't getting any younger, so I decided to settle down. 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 a batch of medals."

"I got married, had a mess of puppies, and now I'm just retired."

The guy is amazed and impressed. He goes back in and asks the owner what he wants for the dog.

"Twenty bucks," the guy says.

"Twenty dollars? This dog is amazing! Why on earth are you selling him so cheap?"

"Because he's a BS'er. He's never been out of the yard."