My Son's Male Cat (unneutered) Is Drooling And His Teeth Are Chattering So Bad My Son Says The Cat Cannot Eat. He Is An Indoor Cat And Has NOT Been Outdoors. There Seem To Be No Other Symptoms. Has Anyone Ever Heard Of This?

The drooling can be a sign of pain or nausea.  The teeth chattering can be a sign of pain in younger animals.  Trauma, toxin exposure, primary gastrointestinal problems, or other metabolic diseases are possible.  This cat needs to be examined by a veterinarian to determine the cause and start appropriate treatment.