Everyone Is John is an excellently crafted CC BY 4.0 game system by Michael Sullivan, originally released online in 2002. It is also, by its own admission, a game for "horrible people", where players all take turns controlling one character.
Players take on one of the several fragmented personalities trapped in the malfunctioning construct Doodad's head, vying for control over the automaton's body and seeking out their personal goals... before it inevitably runs out of juice and the whole process starts all over again. Collectively, as Doodad, players will collaborate (or infight) their way through their surroundings, adapting and developing a more concrete sense of self by gaining new shared attributes that stick around across sessions.
Game Masters, in turn, can run a Doodad campaign in whatever setting feels best--though the decidedly robotic nature of the protagonist fits in well with a fantastical or science fiction based story--and pit players against each other and the world around them, encouraging both collaboration and opportunistic back-stabbing as everyone shares the same body to achieve their individual goals.
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This TTRPG hack was put together for the first time in print for the One-Page RPG Jam, and utilizes a zine format I try to use in most of my more recent works! The front side contains all the rules, with the inner side containing a blank character sheet. For help folding a zine, see here.