fast dog

this man is driving down the road in his new car, and he see's an old man trying to thumb a ride, and the old man has a dog with him. he feels sorry for the old man, so he pulls over and roll's the window down and says to the old man, hey buddy i can give you a ride, but i cant put a dog in this new car. the old man says, oh thats no problem, the dog will keep up with us. the man thinks to himself yea right, and they take off. he gets up to forty mph. and looks over at the old man and says, hows the dog doing? the old man says he's right here by the door. so he speeds up to sixty mph. and says hows the dog doing? the old man says he's still here by the door. the man speeds up to ninty mph. and says hows the dog doing now? the old man says, he's still here by the door the man slams on the brakes and comes to a sliding halt, and says theres no way that dog is still there, he runs around to the other side of the car, and sure enough the dog is still there. the man says, my gosh he really is there, but whats that ring around his neck? the old man says, well he's never stopped that fast before, that's his butt hole.