New Super Mario Bros. Wii has barely been out 48 hours, already there's a level editors for it, and already someone's rebuilt World 1-1 from the original Super Mario Bros.
This might be played through a Wii/GameCube emulator, not on the console itself. There are a few flaws in the re-creation - how many can you spot? Mario doesn't go into the subterranean coin chamber, but that doesn't mean it exists, so let's say that one doesn't count.
Fan Recreates SMB World 1-1 in NSMBW [The Tanooki]