Is an idea that has been tumbling around in my head for a while. It's a social abstraction of the regular game.
Instead of a group of players with their own characters, the characters are set. They have guidelines on how to play them, but every week a new person controls that character.
For this to work the characters I think should be as tropey and stereotypical as possible, say like a Simpkin rogue, or Gandalf wizard.
And after each session, the exploits of the character get added to the make up of that character going forward.
ie; player #3 runs Mad Skillz the half ogre bard for a session and decides that he has felt an inspiration and abandoned his rapper roots and embraced the tin whistle. Next session that's now part of his character.
The biggest problem with it is that it frequently seemed to turn into a contest of writing a character into a corner just to see how the next writer would get them out of it.