... just kidding.
So, actually, what we have here is an idea blatantly stolen from this thread. I decided that since having a giant map seemed pretty funny, then obviously the opposite, a tiny map, would be hilarious. I actually started putting it together as a joke (since you'd be stuck in the ceiling right at the start of the map) and then from playing around in it using noclip an idea formed of an actual playable map at 1/4 scale. This is the result.
If you guys could play test it for me, that'd be grand, since I've never actually completed it without cheating...

WARNING! READ THIS FIRST! This WAD requires Doom 1 and the latest SVN version of (G)ZDoom to play! It will not run in ZDoom 2.2.0, as it uses SVN-only features to avoid having to redistribute modified graphic assets along with it. It will run in Doom 2, but there will be missing textures and the music will not be correct. You have been warned.
Anyway, let me know what you guys think.