So a cop is walking down the street, and up ahead he sees two boys in a wagon, being pulled by a dog. They have their full Fireman gear on, coats, helmets, garden hose, little ladder, etc.
The dog suddenly howls, and sprints for about 30 feet.
As the cop gets close, he sees the kid in front give a yank on a string, the dog howls, and sprints again.
Now the cop can see the string is tied to the dog's testicles.
He stops the dog, and says, "Now boys, that's not right. You can't treat your dog like that! Take that string off now, or I'll have to tell your parents.
He watches the abashed boys untie the string and tuck it in a pocket. They get back in, and get the dog going again.
As the cop turns to continue his patrol, he hears one boy say to the other, "Damn, we lost our siren and our passing gear!"