There was a patient who thought the food trays were alien devices. He would carefully examine them and then try to 'disarm' them by poking at the food with his fork. It was so funny to watch his serious face as he did this.
Sure. There was a patient who thought he could communicate with plants. He would spend hours talking to his potted flowers, believing they were giving him advice on life. Another one was a person who was afraid of odd numbers. Every time they saw an odd number, they would feel a sense of unease and try to avoid it.
Sure. There was a patient who thought he was a famous singer. Every day he would hold an imaginary microphone and sing at the top of his lungs, even during group therapy sessions. It was hilarious because his 'performances' would sometimes make the other patients forget their own problems and just laugh.
Sure. There was a patient who thought he was a superhero. One day, he tried to 'fly' off the balcony of the hospital's rec room. Fortunately, the nurses caught him just in time. He then said his powers were just 'charging up' that day.
One of the most interesting funny psych stories I know is about a child who thought that his toys came to life when he was asleep. He would leave out little treats for them every night. Another one is a man who believed that his car had feelings. He would talk to it, apologize when he hit a bump too hard, and even sing to it on long drives.
Definitely. There have been accounts of poor sanitation in some psych hospitals. Dirty rooms and unhygienic conditions can be very distressing for patients, not to mention the potential health risks.
There was a patient in the psych ward who had been wrongly diagnosed. He was put on medications that made his condition worse instead of better. His family visits became less frequent as they thought he was just being difficult. He was really just a victim of misdiagnosis, and his story was a sad one of being lost in the system.
One horror story is about a patient being left alone in a cold, dark room for hours without proper medical attention. The staff just ignored their calls for help.
The plot could get really meta. Maybe the characters would start to act according to the fanfictions they read, which would be very different from the original plotlines. For instance, if a fanfic had a romantic pairing that wasn't in the original show, the characters might start to develop feelings for each other in the 'real' story.
The most terrifying element is often the loss of a child's innocence. For example, when a child starts to show signs of extreme fear or paranoia that are not typical for their age. It's scary to see them so affected.