Drunk relatives at a family gathering, especially drunk relatives you haven't seen for 25 years and have never been close to to begin with.
We don't really speak to my dad's side of the family often, but it seemed like my grandma's 80th birthday would be a fairly normal affair, with only her sisters, their kids and their grandkids being invited, plus the two sons of her late partner she's on good terms with. Except that my dad's cousin, who is also my godfather, arrived too, despite my grandma's explicit request that he be stopped from entering unless he can sober up. Problem is, his sister couldn't muster the willpower to make him stay at home, and my grandma is also too much of a pushover to keep him out now that he was there. Despite him having arrived visibly drunk (and bleeding all over the place because he had the bright idea to shave while in that state), the restaurant kept serving him, and my grandma compromised by requesting that they only serve him beer as if that helped. When he left for one of his countless rounds at the bar, my mom loudly complained to my dad's nieces that his cousin wasn't supposed to be here and that he was making everyone uncomfortable, and got the all too sympathetic response of "you'll survive a single birthday, we have to listen to his bullshit every day, now it's your turn", but apparently he's "not that hard to handle once you get used to him". He was sat next to us and then kept subjecting us to his drunken antics and just generally making a scene, with his sister, the one responsible for him being there in the first place, only telling him "no one gives a shit what you say", after which she proceeded to ignore him for the rest of the gathering, visibly relieved that he had finally found someone else to bother. By the time he started yelling about wanting to watch pictures of certain body parts on his phone, my relatives realized they couldn't just dump him on us, so they decided that if he's going to make a scene anyway, they might as well get some fun out of it, so they started to egg him on. You can guess how that went.