Hospitals, the only place where positive is a bad thing. There's hospital humor all over the web. A lot of them are about Doctors and nurses and their interactions with patients. "When I find out my patient is on isolation precautions after I've already been in the room a million times." Or, "Remember the hospital staff is here to help you. And laugh at your wang while you're under anesthesia."
One joke we can all relate to about going to the hospital is when the Doctor comes in and asks you what hurts then applies pressure to it. Hey! I said that hurts! As the doctors would say about the people, "I've got 99 patients and an insured ain't one!" For the positive people, "Being in the hospital is a downer, but there is good in everything. You're being served breakfast in bed!"