Well, there's the one about someone I know who has OCPD, where she had this thing about not getting hair product on her upholstery. She directed this totally at her stepson, however, and didn't seem to think anyone else wore hair gel. When he came to visit, she'd make him sit in a certain chair that had an antimacassar on it, but like, whenever he moved she'd be following him around the room with this antimacassar just in case he sat down on any other chair, and then the piece de resistance was when she put it on the back of his chair at the dinner table, even though the back of the chair only came half way up his back, nowhere near his hair. That was pretty funny from the fly on the wall POV...
Then there's the guy I know who needed to open a new bank account. To open this bank account he needed two forms of ID with his address on them, such as phone and utility bills. However, all of his phone and utility bills from the past 9 years were in a pile on top of his fridge. This is the 'do not touch' pile. Anything that goes on the fridge must never, ever be touched again. It ceases to exist. The reason they're there is because they've been on the floor - of course, when they come through the letterbox they land on the floor (we don't have those weird outdoor mailboxes like you do in the US, we have letterboxes in our front doors here!). So he picks them up with tongs that are there for the purpose, and puts them on top of the fridge.
So he calls the utility company and asks them to send him a fresh statement, so he can use it for ID, hoping to catch the mail man when he arrived and take it from his hand. But when he hears the mail man, he's in bed, and doesn't want to get out of bed because he likes being in bed. It's "safe", he says, in bed, and he's notoriously difficult to persuade to get up at the best of times.
So this kept on happening. I offered to pick up one of the things off the fridge and open it for him so he could use one of those. But he said that wouldn't work, because if the letter touched the outside of the envelope it'd be contaminated. I said I'd be really careful not to let it do that, but he said it still wouldn't work, because once I touched the outside of the envelope, I'd be contaminated, and therefore so would anything I touch.
So I offered to come round and fit a cage to the back of his front door so that letters would not land on the floor. But he said no, because there "wasn't time" to buy one. Apparently it'd take him a few months to buy one of those, because he'd have to work his way through a bunch of mental and physical rituals for allowing a "new item" into his house. And he needed this bank account now.
So I said, supposing I come round, take a letter from the top of the fridge with the tongs, put it in a plastic bag and take it outside, walk to the bank with him and give the letter to the clerk. He said that wouldn't do, because if the clerk touched the letter, then she would contaminate his bank card, cheque book and anything else of his that she touched, and not only that, but she might even contaminate him if she shook his hand.
In the end, he had to rent a P.O. Box at the post office - the shortest and cheapest lease was double his weekly income - just so that he could get a utility bill that he could take not from the floor, so he could open this bank account.
The whole farce took around eight months.
Like I say, hilarious - like a sitcom or something, until you think things like this affect everything in his life. If I want to invite him to lunch, it can never be spontaneous - I have to give him at least 24 hours' notice because that's how long it takes him to get through his 'going out of the house' rituals.