This guy is driving down the highway in his corvette and sees a hitchhiker with a big dog. So he stops and tells the the guy he would give him a ride, but there's not room for the dog. The hitchhiker says "I can tie his leash on the back bumper." The corvette driver says "that dog can't keep up." The hitchhiker says "oh yeah, he's pretty fast." So he ties the dog on the back bumper and they get in and take off. The driver gets up up to 20 mph, looks in the mirror and the dog is trotting along behind. He kicks it up to 50, looks in the mirror and the dog is just loping along . So he kicks it up to 80, looks in the mirror and the dog is running all out. He thinks Damn, I gotta take another look at this dog. So he slams on the brakes and they get out and walk to the back of the vette. The dog is just standing there. The driver says "that's the fastest dog I've ever seen. But what's that red ring around his neck?" The hitchhiker says "that's his a$$hole, he's not used to stopping that fast."
