A man was walking on the sidewalk and noticed up ahead Little
Johnny, wearing a red fireman's hat and sitting in a red wagon. It
appeared that the wagon was being pulled very slowly by a large Labrador.
When he got closer to the lad, he noticed that Johnny had a rope tied
around the dog's testicles, which probably accounted for why the dog
was walking so gingerly.
Smiling, he spoke to the little boy, "That's really a nice fire engine
you have there, son. But I'll bet the dog would pull you faster if you
tied that rope around his neck."
"Yes," Johnny replied, "but then I wouldn't have a siren."