My guess is that it was his brother's dog...
A guy is driving down the road in West Virginia and he sees a hand-lettered sign: “Talking Dog for sale – 10 dollars.” He’s curious, so he stops and begins walking up the driveway. He gets close to the house and sees a dog. Joking to himself, he calls out, “Are you the talking dog?”
The dog looks up and says, “That’s me.”
The guy is floored. He can’t believe it. He says, “When did you learn to talk?”
The dog says, “I was pretty much born talking. It freaked people out, so I got abandoned at a young age. I had to live by my wits for a long time. Eventually I made it to Washington DC and bumped into a fellow who worked for the CIA. We teamed up and went all over the world. Turns out a lot of foreign agents will say things to a dog after the official interrogator has left the room. They talked to me, I talked to my partner and we broke open a lot of cases. But eventually I got tired of it and spent a few years traveling the world on my pension. Now I’m too old for traveling, so I just hang out here.”
The guy is amazed. He goes up to the house and knocks on the door. A man opens up and the guy blurts out: “I want to buy that dog! I only have one question – why are you selling him for just $10?”
The man who opened the door says, “Because he’s a damned liar, that’s why. He told you about the CIA, right? And travelling the world? He ain’t done any of that. He’s spent his whole life right here on this farm.”