My brother derailed the first session of my horror campaign
I am the DM for my group and it is my favorite thing to do. I love preparing my sessions almost as much as I like running them. I'd been running DnD for a couple years at that point and Daggerheart had just come out. I really wanted to play it and it wasn't hard to convince my PCs to try a mini-campaign.
They voted on the setting and Age of Umbra won. I was thrilled because horror is my favorite genre. Fall is my favorite season and Holloween was right around the corner, so I was super excited to play a spooky and dark mini-campaign. My only restriction on character creation was to not make a character that would clash with the setting and mood of the game. I told them they could still make jokes and have fun, but don't betray the tone of the setting, especially if I am obviously going through the trouble of building tension.
My brother showed up to play and it turned out he was playing the biggest joke character I have ever seen. He had the name gimmick, over the top joke parody music, the hole nine yards. This immediately clashed with the tone. I had my own horror music playlist I was using and suddenly going from that to a parody song already had me irritated.
Imagine if Austin Powers was dropped into the middle of a movie like Hereditary, Oculus, or Sinister. The tone was killed immediately. His character ended up getting killed in the first session. He made another character mid session and that new character somehow ended up being an even BIGGER joke character than the last one. He was hostile towards the party and it felt like he was deliberately tanking the session with characters that just didn't fit the worldq. I have never been so angry while running a game before.
I am a pretty calm and easy going person. I don't get angry easily. I am very even keel, but after that game I scalded the hell out of him over text since we drove separatelyto where we would play. He didn't want to play Age of Umbra in the first place. He voted for something else and then pouted when it lost during session 0. He didn't want to play Daggerheart specifically because you don't role a D20 as your main die. So I truly believe that those characters were essentially him throwing a hissy fit like a child because he didn't get his way. This was back in late September-October and I still get mad when I think about it
Edit: I did have a Session 0. That's when we decided which setting we would use. He picked a different character, but called me later to ask if he could change it. I told him as long as it doesn't clash with the tone I didn't care. I guess I just trusted him too much