I don't have enough stupid in the dungeon yet.
a. Subsurface Circus
So... here's something for the ninth level. Near the 9th level entrance, past the cave kraken that's been chewing on all those poor soldiers of the Unyielding Fist, there's a hangar, containing a single Avro Lancaster bomber. Everything is in perfect condition - all the rubber parts are pliable, the fuel is fresh, etc. There is also a manila envelope marked TOP SECRET, containing orders for the missing crew - to destroy the Nazi Time Ray before it can be used to modify history. Location: Hitler's Bunker.
If the plane is wheeled out of the dungeon and the airstrip outside the 9th level entrance cleared, it can be flown off - where it will instantly pass through a time portal back to 1943, over Berlin, and presumably be shot down. The Nazis will be unsure of the effects of their Time Ray since the plane only disappeared for a moment, and will send a bunch of SS thugs to capture and interrogate the crew. From there, the players must fight their way back to the Time Ray and defeat Hitler to return home. Or whatever else they want to do. Maybe find Glenn Miller and join the band? Who knows...
The circus is going over very well - I was wondering if the players would rebel at the sheer ridiculousness of an underground carnival. They're actually quite enthusiastic, and paranoid about the massive numbers of Painted Men turning on them unexpectedly, so it's working out exactly as I had hoped. Given that success, it's full steam ahead on my other stupid ideas.