Talking dog

A guy is driving around the back woods of Montana and he sees a sign in front of a broken down shanty-style house. 
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Talking Dog For Sale. 
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He rings the bell and the owner appears and tells him the dog is in the backyard. 
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The guy goes into the backyard and sees a nice looking Labrador Retriever sitting there. 
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You talk?  he asks. 
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Yep, the Lab replies. 
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After the guy recovers from the shock of hearing a dog talk, he says 
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So, what's your story?         
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The Lab looks up and says.
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Well, I discovered that I could talk when I was pretty young.
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I wanted to help the government, so I joined the CIA.  
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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 eavesdropping.
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I was one of their most valuable spies for eight years running.
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But the jetting around really tired me out, and I knew I wasn't getting any younger so I decided to settle down. 
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I signed up for a job at the airport to do some undercover security, wandering near suspicious characters and listening in. 
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I uncovered some incredible dealings and was awarded a batch of medals.
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'I got married, had a  mess of puppies, and now I'm just retired.
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The guy is amazed. 
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He goes back in and asks the owner what he wants for the dog. 
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Ten dollars, the guy says.
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Ten dollars? 
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This dog is amazing!
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Why on earth are you selling him so cheap?' 
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Because he's a liar.
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He's never been out of the yard.