Greatest Easter Eggs In Gaming

For those who don't play video games - or have never played a game enough to find one - "easter eggs" are the little secrets hidden in a game for persistent users to find. Gamespot recently posted an article entitled "The Greatest Easter Eggs In Gaming", and it was fun to reminisce over some of them. The cow level in Diablo II has got to be one of my all time favorites. Diablo II was a action RPG about fighting demons will huge swords and the like. So having a hidden level that was full of evil cows that continually bleated "Moo" while they attacked you was just hilarious. Finding Reptile in Mortal Kombat was also another of those awesome easter egg moments. Does anybody else remember any great gaming easter eggs?