Someone has created a mod for Super Mario on the NES, and to be quite honest, playing it would have made me go into a long rant filled with so many expletives, even the Angry Video Game Nerd would have disapproved.
http://www.kotaku.com/gaming/clips/clip-most-diabolical-super-mario-mod-ever-251735.php
http://www.kotaku.com/gaming/clips/clip-most-diabolical-super-mario-mod-ever-251735.php