The little girl is wearing a fireman's helmet and has the cart tied to a dog and a cat. The fire-fighter walks over to take a closer look:
"That's a lovely fire engine,' he says admiringly.
Thanks,' says the little girl.
The fireman looks closer and notices the little girl has tied one of the cart's strings to the dog's collar and one to the cat's testicles.
'Little colleague,' says the fire-fighter, 'I don't want to tell you how to run your fire engine, but if you were to tie that rope around the cat's collar, I think you could probably go a lot faster.'
The little girl pauses for a moment, looks at the wagon, at the dog and at the cat, then looks into the fireman's eyes and says:
'You're probably right, but then it wouldn't have an 'effin siren, would it?'