A man spots an ad in the For Sale classifieds for a talking dog for $10. This he has to see so he pays a visit to the guy selling the dog. Upon arrival, the guy sends the man round the backyard where he sees the dog sitting on the lawn. Sure enough, the dog starts talking and soon the dog's life is borne out:
"I used to work as a police dog and when they found out I could talk they moved me to the undercover division doing drug busts and catching smugglers at the airport. They never suspected the dog. Then I started working in intelligence as a spy, travelling the world, eavesdropping and getting all sorts of information. No-one ever suspected the dog. That all got a bit tiresome so I came back here to find a partner and settle down, have some pups."
The man rushes around the front and asks the guy why is he selling the dog so cheap. The man replies "He's a liar, he never did any of that undercover spy stuff".