The-Magic-Sword
Small Ball Archmage
True, a similar but more canonical example might be the emotions of a GM who develops great affection for a worldbuilding element, and is going for a certain vibe with that, who might need to negotiate their player's differing expectations to preserve the relative sanctity of what they creatively wanted out of that element.I had wondered about Microscope as an example, but wasn't confident in my knowledge of it - so I am glad you mention it.
But as I understand it Microscope is quite far from paradigmatic RPGing, in that the game doesn't progress primarily by players declaring actions for the particular characters (i) who are part of the shared fiction, and (ii) whom they own. So it makes sense that it wouldn't literally involve OCs.
Like, presenting an order of knights or something that are supposed to be the good guys in terms of what the vibe the GM was trying to enjoy was, but the players push to make the campaign about rebelling against them, or reinterpreting them as corrupt. That would be a very similar conflict as we understand OC as being in conflict with the other cultures.
The point is, that other elements can take on the sense of ownership associated with OCs, though 'creating a character' creates a natural outlet for that urge, so 'I own another element I introduced to fiction, but not my character' is improbable, but not impossible.