Last Tuesday I went to see a documentary about M.C. Escher in a Science Museum, and it reminded me of that Taxing 18 level of original Lemmings, titled "Tribute To M.C. Escher". Where is the tribute to him in that level? Maybe in the simmetrical solution to it that uses bridges?
I think it's simply in that the level involves a lot of stairs - after all, Escher's most famous work is that crazy staircases one.