Counterfactuals and Games of Make-Believe
In chapter 10 of The Varieties of Reference, Gareth Evans endorses a counterfactual analysis of truth in games of make-believe: When children play the mud pie game, an utterance of "Harry placed the pie in the oven" is true (in the game) iff (roughly) it would be true given that these globs of mud were pies and this metal object were an oven.
He then notices that this is a problem for the possible worlds analysis of counterfactuals because the relevant counterfactuals seem to have impossible antecedents: "there simply are no possible worlds in which these mud pats are pies" (p.355).
One solution -- at least a solution for those that don't believe in literal trans-world-identity -- is to alter the relevant counterpart relation so that other-worldy pies come out as counterparts of the mud pats. This might work, but it is not very satisfying.
For consider games of make-believe in which the players pretend that there is something that is not represented in the game by any concrete object. If, for example, there is no suitable metal object around, the children in the mud pie game might just pretend that there is an oven at some place where in fact there is nothing. So are the other-worldly ovens counterparts of nothing, or of regions of space, or air? This doesn't sound promising.
The more general solution is to understand the entire game as an implicit, and partly non-verbal, specification of a class of worlds. The correspondence principles between mud pats and pies, pebbles and raisins etc. allow for non-verbal descriptions: By arranging the mud pats in a certain way you describe the make-believe worlds as being such that the pies are arranged in that way.
So the general analysis of truth in games of make-believe is something like this: An utterance of p is true in a game of make-believe if the corresponding utterance by the speaker's counterpart in the closest world among those specified by the game is true.
This also nicely accounts for demonstrative utterances in a game. By pointing at the empty region of space and saying "the pies are in that oven", you can say something true (in the game) because the counterpart utterance in the relevant game-worlds is true.