Have you seen "The Great Bear"? It's a cute version of the tube map with altered station names. A sample: http://www.dareonline.org/artwork/patterson/patterson3.html. (Found at "Life and Times of the London Underground Map" http://www.bbc.co.uk/dna/h2g2/A673517.)
I have indeed. I believe I even took part in a game of Mornington Crescent on it once.
(All Sinologues declared mauve.)
tube map alterations: funny
ps. impact! eeeeeyyywwww! unless one has a 23 inch monster monitor. it's frankly damn hard to read.