Un video del bug:
http://www.youtube.com/watch?v=FC60CDEJRgA
Minus World
World -1 (A.K.A. the "Minus World") is an infinitely-long water level, only accessible through World 1-2. Here's what you do: As Super Mario, get all the way to the green pipe at the end of 1-2. Stand on top of the pipe and smash the blocks above you. Do not smash the very last block on the right. Now, stand on the end of the pipe and face left. Jump straight up, then press and hold Right on the controller. What you are trying to do here is jump through the bottom left corner of the block backwards. If you do it just right, Mario will slide through the block and be pulled through the wall. When Mario gets to the other side of the wall, go down the first pipe before it says "WELCOME TO WARP ZONE." You will not come out in 4-1, but in -1. Yes, that's right, -1. World -1 is just like 2-2, but the pipe at the end takes you back to the beginning. You cannot beat -1, but it does give you lots of swimming practice
Side note: If you go down them before it says "WELCOME TO WARP ZONE," the second pipe takes you to 5-1, and the third pipe also takes you to the Minus World.
In the Famicom Disk System version of SMB, the Minus World is a swimming version of World 1-3, with gray enemies, pink platforms, and a floating Bowser. At the end, if you touch the flagpole too high, you'll float over the castle door and won't clear the level. Touch it about halfway down to be safe, and you'll drop right into the door, taking you to World -2! World -2 is exactly like World 7-3, except beating the level takes you to -3. World -3 is like 4-4, except it's not a maze, there's no Bowser at the end, and the graphics are blue instead of gray. After you touch the axe at the end, you are thanked as usual, but the Mushroom Retainer is not there. Press B, and you are taken to the title screen, where you can keep pressing B to choose a World to go to, with harder levels, exactly as if you had just beaten the game.
Fuente:
http://www.themushroomkingdom.net/smb_bugs.shtml
Tal como dijeron, el juego es port 1:1, pro lo que tendra el bug