He wanders out to the road and flags down a ride, which just happens to be a Ferrari. The driver says, "You can have a ride, but that dog can't get in my car."
the farmer says, "Don't worry. Old Joe will keep up."
the driver figures he'll show the farmer just what his car can do and lets it rip. Just as he is going into 5th gear, he looks out the window and sure enough Old Joe is right beside him. He can't wait to have a look at the amazing dog, so he slams on the brakes, and the car stops rather abruptly.
the driver jumps out of exclaiming, "He's the most incredible dog I've ever seen! But what kind of collar is that he's wearing?"
the father shook he said and said, "That's not a collar. That's his asshole. He's not used to stopping that fast."