King Arthur returns from the dead in accordance with legend, but is now completely unqualified to lead due to having missed the last millenium of political and technological progress (sort of like a combination of the constitutional peasant scene from Monty Python & The Holy Grail with the future shock/culture shock scenes of the first Austin Powers film
King Arthur, King Harold, Robert the Bruce, Finn MacCool, Emperor Nero, Bran the Blessed, Owain Glyndwr, King Olaf I, Vlad III, Sir Francis Drake, Emperor Norton, and JFK (i.e., many of the "king sleeping under the mountain" figures) revive simultaneously on the outset of the third world war, and get into a great drunken brawl in a dive bar.
The King(s) Under the Mountain(s) are awoken when mining and deforestation remove the ravens and eagles etc. circling the mountaintops
A story with a premise similar to The Purge
, ie. there's an annual festival where all crime becomes legal. In this reimagining however, most people spend purge night at work. The corporations pay all their workers overtime and hazard pay to come in and spend the entire day destroying documents and other evidence proving criminal activity, as well as records that they are supposed to keep but cost money to maintain and store.
The problem - Invasion by alien monsters that sense fear
The solution - lots and lots of PCP