I once had a roommate in the basement who basically never left his room. He used to wear some kind of gloves at all times, and was once seen outside at around midnight going to the nearby park with a garbage bag full of who knows what. We joked that he was some sort of a serial killer, but in reality the poor guy probably just had a fair amount of mental health issues.

In another apartment the landlady looked like a stereotypical brothel madam. Sort of old, lots of make up on and a big hair. Whaddayaknow, we had a prostitute ring going on in the building. Lots of strange, nervous dudes waiting at the door late at night, young women with a lot of make up and skimpy clothes coming and going with suitcases… Until one day there was police tape over a handful of the doors and the picture of our apartment building in the local paper. At least our next door neighbor was a lovely old man who still sends us cookies that taste strange and are borderline edible - but the gesture is terribly nice. Good times!

Edit: Thanks OP for doing a question like this here. Of course it’s ok to ask technical questions, but they are just a lot more boring than real life stories - I hope we get them going and I never have to go back to askreddit.