via http://gbatemp.net/t297001-mario-adventure

This hack has actually been called "the greatest SMB3 hack of all time." The hack includes many boss battles, changing weather patterns, new power-ups, time-stopping potions, invisible Mario, and a market system so you can actually spend your coins. Worth a patch? Give it a try and let us know what you think!

http://www.romhacking.net/hacks/70/