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the loner. People want to channel Aragorn at the prancing pony but it's just annoying. It's a group game. Play with the group.
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the outsider. The one that doesn't fit in. Like you're playing a dungeon crawl so someone makes an accountant with no combat skills. You're playing a game about vampire hunting in Louisiana and someone makes a character that doesn't believe in vampires that's from Spain.
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related to the above: the absolute newbie. You're playing a game of vampire focused on intrigue and plots. Someone makes a character that was embraced yesterday. They don't know anything about anything. A constant stream of "we need to drink blood?? You can turn invisible??"". It gets boring real fast. Or, you're playing a sci-fi future game and someone wants to play a 20th century man who was just unfrozen, and doesn't know anything about the 23rd century.
The theme I'm trying to nail down there are characters that don't really engage with the game's premise. They're characters that could exist in the world, but are for this game don't really belong.
I think people see Bilbo from the Hobbit and want to channel that "party boy out of his element" energy but it usually won't work. Or fry from Futurama. You're playing a game not writing a book. Don't take extra spotlight. Don't be incompetent.