A firefighter is working on the engine outside the station when he notices little johnny next door in a little red wagon with little ladders hung off the side. The boy is wearing a firefighter's helmet and has the wagon tied to a dog and a cat.
The firefighter says, "Hey little partner, what are you doing?"

little johnny says, "I'm pretending to be a fireman and this is my fire truck."

The firefighter walks over to take a closer look. That's sure is a nice fire truck," the firefighter says with admiration.

Thanks mister," johnny says.

The fire fighter looks a little closer and notices that johnny has tied the wagon to the dog's collar, and to the cat's testicles. The boy says, "You're probably right, mister, but then I wouldn't have a siren."