One of the rules at my table that I enforce is “Make it boring”, because I’ve just noticed that every time someone shows up with a theater kid OC they are frustrated by how hard it is to roleplay, frustrated that they don’t get to run into much stuff related to their backstory, and generally just have an overall tough time letting their character grow past the first session because they already got attached to the character before the game even started. They also struggle massively with character death.
Ever since telling everyone to make it boring, yeah we start with 4 humans if various classes and a dwarf, but they tend to have more fun as those characters are able to grow mid-game and develop as they play.
It kinda bleeds over into everything. For example I run a little Hierloom system where character deaths usually result in a cool magic item customized to the character. Theater kid OC characters usually had the player wanting me to base the effect off their backstory, since that’s what they’re attached to, but I’d have to explain that nobody else at the table actually gives a fuck about their backstory but them. Meanwhile, my player’s favorite item ever was because it was born of a tank character’s resolve to take care of the party’s favorite NPC
Laughs aside, even with the basics of Urban Operations this is a great example of why the US military trains to have a guy watch the rear at all times.