Have a room in your dungeon that you don't know what to do with? How about creating the laziest room ever? Once the characters walk through the door, they are greeted with a bizarre sight; describe the room that you are playing Dungeons and Dragons in. The characters see their players sitting at a table, they can see their lips moving, but they can't hear what they are saying.
Now, here is the gag: The characters can pick one object from your gaming room, and take it with them. Once they take an object, they disappear and return to just an empty room in your dungeon. We can then design an enchantment for the object and how many times that they can use it before the object disappears.