A farmer is in the middle of plowing his field when his tractor runs out of gas. He needs to get back to the farm, but it's too far for him and his dog, Old Joe, to walk.
He wanders out to the road and flags down a sports car. The driver says, "I'll give you a ride, but that dog can't get in my car."
The farmer says, "Don't worry. Old Joe will keep up."
The driver decides to show off and open up the engine for max speed. Just as he's going into fifth gear, he looks out the window and sees Old Joe right beside him. In amazement, he slams on the brakes and Old Joe comes to a halt.
The driver jumps out, exclaiming, "He's the most incredible dog I've ever seen! Is there something special about that collar he's wearing?"
The farmer shakes his head and says, "That's not a collar. That's his a**hole. He's not used to stopping that fast."