Bad HP idea from my bad brain that won't quit:
Draco Malfoy runs a D&D game with Harry, Ron, Hermione, and Luna as players. Harry's the paladin. Luna has the elf-mage character with a 50 page background. Hermione's the rules lawyer playing a thief that won't steal or pick locks. Ron complains because he's gotten stuck with the cleric. All this in the Tomb of Horrors with a DM who wants to kill the party.
Once again, this writes itself.