Super Demo World: The Legend Continues
Pay no attention to the word ‘Demo’, this is a full game.
To say this is the greatest romhack ever would be doing it a disservice. This is a whole new Mario World. New plot, new palletes, new world map, new Star World, new (if stolen from previous Mario games) enemies, region-specific Ghost Houses (World 2 is a pyramid!), several types of block from Mario 3 introduced (remember the white Note blocks?) and everything at least one order of magnitude harder than the original was. And several stages are exact copies of the stages of Super Mario 3!
They could have seriously wrecked this, but damned if this guy didn’t pull it off. Get the SMW US version, get IPS.exe, patch it and play this. Seriously. You won’t regret it.