Here is the first version of Kens Labyrinth called "Walken", made by Ken Silverman who also created the Build Engine.
On his website the file is dated 09/20/1992. Comes with source code.

Download - walken.zip
Link to source of original file - http://www.advsys.net/ken/klab.htm

I decided to take a look into it and it is vastly different from the final product. Pretty much everything is different when compared to the final; enemies, graphics and the like. A few of the final's cheat codes work, but there doesn't seem to be any way to give yourself more health, which makes some of the levels pretty damn difficult. It contains about 11 levels and the game crashes if you try to access any level past 11. There is an early version of the final's lightning weapon, but I can't seem to find a way to use it. The only usable weapon available is some sort of bubble gum/fire ball thing which can be automatically fired by holding down the fire key.

I think Ken is right when he says that this was supposed to be a demo from companies interested in it; the gameplay is very barebones (only one enemy AI behavior), the graphics are very primitive, all of the sounds are just Ken and his buddy Andy talking and making noises, and the maps are horribly unbalanced (there are like 2 healing items per map and enemies are everywhere). It would be unsellable in the state it was in this prototype. However, it is still impressive, considering it was programmed by a junior in high school on his own soon after Wolf 3D came out.