I like the Medieval Homestuck idea.

So, our heroes are eagerly awaiting copies of a manuscript that details the rules of an exciting and ingenious new boardgame. They're going to play it as a correspondance game, each sat in their own guardian's manor house and sending homing pigeons to the other players with the details of their moves. The game's complex rules seem to involve both strategy and chance, and some elements recall the novel game of "Chess" that has recently reached Europe from Hindoostan. It has an elaborate setup phase. Hark at their surprise then, these precocious moppets, when the opening moves cast them bodily into a strange realm of fairies, angels and demons!