An old tired-looking dog wanders into a guy's yard. He examines the dog's collar and feels his well-fed belly and knows the dog has a home.
The dog follows him into the house, goes down the hall, jumps on the couch, gets comfortable and falls asleep. The man thinks its rather odd, but lets him sleep. After about an hour the dog wakes up, walks to the door and the guy lets him out. The dog wags his tale and leaves.
The next day the dog comes back and scratches at the door. The guy opens the door, the dog comes in, goes down the hall, jumps on the couch, gets comfortable and falls asleep again. The man lets him sleep. After about an hour the dog wakes up, walks to the door and the guy lets him out. The dog wags his tale and leaves.
This goes on for days. The guy grows really curious, so he pins a note on the dog's collar: "Your dog has been taking a nap at my house every day."
The next day the dog arrives with another note pinned to his collar: "He lives in a home with four children -- he's trying to catch up on his sleep. Can I come with him tomorrow?