The humorous illnesses that appear in Theme Hospital include:
- Slack Tongue - caused by chronic over discussion of soap operas; treated by cutting off the enlarged bits with a Slicer Machine.
- Broken Heart - caused by jealousy from contact with someone richer, younger, and thinner; treated by surgeons mending the heart.
- Transparency - caused by licking foil tops of yogurt pots, turning the body see-through; a fictional humorous illness.
- Bloaty Head - caused by sniffing cheese and drinking un-purified rainwater; treated by popping and reinflating the head with a machine.
- Infectious Laughter - caused by watching classic situation comedy; treated by a psychiatrist reminding patients of the seriousness of the condition.
- Hairyitis - prolonged moon exposure causing extreme hair growth.
- Fractured Bones - a common humorous illness treated in the fracture clinic.
- Serious Radiation - caused by radioactive exposure.
- King Complex - the spirit of the king entering the mind causing ridiculous behavior; treated with psychiatry.
- Sweaty Palms - fear of job interviews; treated by psychiatry.
- TV Personalities - delusions of presenting a cookery show; treated by psychiatry.
- Golf Stones - poison gas inside golf balls causing delirium; treated with surgery.
- Iron Lungs - inner-city smog mixed with kebab remains causing strange symptoms; treated with surgery.
- Invisibility - caused by being bitten by radioactive invisible ants; patients play practical jokes during condition; cured by a colorful liquid.
- 3rd Degree Sideburns - longing for the 1970s causing big hair and glitter makeup; treated with psychiatry.
- Fake Blood - red fluid in veins evaporating on contact with clothing; treated by calming psychiatry.
These illnesses are fictional, comical, and part of the game's quirky charm, making Theme Hospital a humorous hospital management simulation.
