A man goes to a dog breeder to buy a guard dog only to be presented with a scruffy terrier mongrel. "What use is that?" he asks. "Don't be fooled. This dog is a trained killer." promises the breeder. "Here, watch this," and he commands the dog, "Guard dog, that chair!" And within a few seconds, in a blur of snapping teeth and yapping, the chair is reduced to splinters. "That's amazing!" exclaims the man. "Can I have a go?" "Sure, try it out." replies the breeder. The man clears his throat and says in a clear voice, "Guard dog, that box!" And within a few seconds, the box has been shredded to mere fluff. Delighted, the man buys the mongrel and rushes home to show his wife. "Look at our new guard dog!" he says. "He's a trained killer!" "What, that scruffy thing?" scoffs the wife. "Guard dog, my arse!"