I have two, both happened in the same semester. The first happened like a week into the semester. One of my roommates (who behaved 100% normally in the previous semester) took shrooms and basically had a mental breakdown. He came out as gay to us (odd because he was genuinely telling us about a girl crush just a few days before) and he was having a panic attack over what other people would think. Me and my other 2 roommates hung out with him and played Mario Kart that night just to calm him down. We thought everything was okay until he pounded on MY bedroom door at 3AM and asked me to take him to the hospital because his heart was still racing. Even though I had class in the morning, I didn't have a choice so I took him, and the doctor checked him out and had him talk to a social worker. They took him to a mental health clinic and he stayed there for a week until his dad came to pick him up. He moved across the country and I only talked to him a few more times after that. He's still a good guy but maybe the stress of college wasn't the best fit for him. TL;DR Roommate took shrooms, had panic attack, got driven to hospital at 3AM, stayed in mental health clinic for a week, and left college.

The second story is about the guy who replaced him. This guy was a total wanna-be bro douche. He put a flag of our rival school in his bedroom window, and he wanted to be a frat boy so bad he would wedge our common room door open (without any of his roommates' permission) and cook awful pancakes every day just to try to be the cool guy. Oh, and he was about 5'4 but he acted like a some tough guy. Anyway, me and another roommate who I was good friends with decided to slowly drive him insane over the course of the semester. We would pour a shitton of salt in his pancake mix so that they would turn out even worse, and we would hide his shit that he left lying around in the common room (we'd put stuff under the couch or in the cabinet above the fridge where he couldn't reach without a chair). When he couldn't find his stuff, I'd hear him flip out and frantically search the common room from behind my bedroom door. Eventually he left a (hilariously) angry note on the fridge demanding that people stop moving his stuff around or else he'd kick their ass. But the funniest thing is that he never figured out it was us. Every conversation we had with him was pleasant and he never mentioned his stuff being hidden. He probably suspected one of his open-door "guests" was hiding his stuff. TL;DR Replacement roommate was a wannabe frat douche, so we mentally tortured him for a semester.