Feeling that Super Mario Bros. lacked in user-generated content, the folks over at SelectButton decided to start randomly inserting text into the Mario ROM (yarrr) and see what happens. Apparently the game is stable enough to run decently with junk added to it, and the results are ... playable and strangely beautiful. Random invisible blocks, palette changes, bizarre sprites, Mario's freaking head is on upside-down, etc.
It's pretty significant that some minor shot-in-the-dark hacking can end up generating new Mario levels that instantly make a near-perfect game infinitely more fun. They should be doing this at I am 8-Bit. If only we could do this kind of user-generated level design on the Virtual Console,we'd have a compelling answer to Sony's LittleBigPlanet. Go ahead and argue with us on that point. We <3 Hacked Mario.
Wii Fanboy does not endorse the use of copyrighted ROM images. Just go gawk at the screenshots for a while; that should be enough entertainment.