Kids jokes-The little fireman

One day a fireman was washing his fire engine and conscious of someone behind him turned round to see a little boy with a fireman's outfit on sitting in a little cart he had painted red.
He had a rope tied round a dogs neck and a rope tied round a cats testicles.
The fireman said to the boy that his cart would go faster if he tied the rope that was round the cats testicles round the cats neck.
The little boy thought for a moment and told the fireman the cart would go faster but then he wouldn't have a siren.