The only reason that sharks can pretend to be fish is that there is real fish out there, that make it an expected win to deviate from nash equilibrium. The fish are not a property of the game, but rather a property of the playerbase.

You can still use game theory to analyze the game though, if you "include" the player model into the game model.

"Rock-paper-fool goes like this. First a coin if flipped without you seeing If tails, you face a fool npc, who will play according to..., if head, you face a (homo economicus) player"

You could then try to analyze the equilibria of this game.