- Demonic Spiders: Epidemics (contagious diseases that have to be vaccinated and cured within a time limit) have a habit of both wrecking you when you're down, and snatching victory away from you when you're just about to win.
- Combined with Unwinnable by Mistake, as epidemics are so annoying because of a particular bug: The idea is that you need to cure all the disease-carriers before they leave the hospital. Unfortunately, "leaving the hospital" includes "walking out any door", and in most levels your wings are arranged in a way that travel between them requires going briefly outside. Unless you block most of the exits (with potentially terrible consequences for pathfinding, not to mention hospital efficiency) and make sure outlying buildings are never used for diagnosis or treatment (which can be impossible on some maps), prepare to get hit with thousands of dollars in fines every few months...
- Earthquakes. Anything that requires maintenance will be severely damaged after a tremor. Sometimes they'll even blow up a room or two in one shot; once a room has irreparable equipment, it's not only forever unusable, but you can't get rid of it. Hiring plenty of skilled handymen is a requirement to combat earthquakes.
- Goddamned Bats:
- Diseases that can't be diagnosed in the "standard" diagnosis rooms (General Diagnosis, Ward, Psychiatry), requiring you to research and buy more advanced diagnosis equipment. Ironically, the more visually obvious the disease, the harder it seems to be to diagnose (Invisibility and Slack Tongue require the X-Ray, Transparency and King Complex the Scanner). One way to combat this is to put your best possible doctors in the GP's office, so they can diagnose as many patients as possible without requiring extra equipment.
- Surgery patients - surgery requires a ward, an operating theatre and two surgeons (sometimes it can be hard enough to hire one).
- Harsher in Hindsight:
- One of the VIPs that can visit your hospital is called "Billy Savile OBE", a parody of British TV star Jimmy Savile. A lot harsher now that Savile has been posthumously accused of sexual abuse - for crimes which were mostly committed against helpless patients in hospitals.
- Another suspect VIP is King Bernhard of the Netherlands. While there has been a Prince-Consort Bernhard, he would have been ineligible unless the rest of the Dutch royal family died out, and possibly even others suchs as the Windsors. Bernhard did live long enough to see his wife and former Queen Juliana die, along with his son-in-law Claus. In the years after, one of his grandsons relinquished his right to the throne to marry and was later buried in an avalanche, dying some years later while in a coma. This is not helped by his 'controversial' history, one urban legend claiming he wrote to Adolf Hitler offering to rule the Netherlands as a German protectorate.
- Nightmare Fuel:
- The game can get particularly unpleasant at times. The player will get used to cheering whenever a patient is cured. It is incredibly jarring to the point of a Jump Scare when a patient is treated incorrectly, as there is booing before the patient leaves the room. Only after they pay and leave the room do they die (and that is usually humourous), but the warning that you've killed them is rather frightening.
- The cutscenes that show after failing a level are universally quite scary.
- Some of the treatments for ailments like Bloaty Head and Slack Tongue look very painful. Not to mention imagining what would happen if the doctor popped the head and then the Inflation machine didn't work...
- There's also the matter of the auto-autopsy machine, which speeds up research on a particular ailment, by feeding a patient through it while they're still alive. And they don't seem to be aware of anything until its too late. Predictably, your reputation drops like a rock if the machine is found out.
- Scrappy Mechanic: The fact that a room can't be used once a machine inside explodes is a very unpopular mechanic among fans of the game.
YMMV / Theme Hospital