Apparently, the original "Super Mario Bros." has way more levels than 32 or so. It has hundreds of them! Those levels are hidden away in every cartridge that is gathering dust in the boxes at our homes. They also weren’t intended to be found as they are “broken” and messed up. For example, there are enemies that have no place within them, like a Goomba underwater… However, some Nintendo enthusiasts have cracked the process and were able to unlock these hidden levels. Here is how you can do it.
There's one well-known secret world in the original 'Super Mario Bros.' — it's called the 'Negative World.'
It's just one of many of the hidden levels contained in "Super Mario Bros.," and it's perhaps the most widely known. You can reach it by performing an awkward backwards jump in the game's second level, 1-2, like so:
But that's just the beginning. There's a far more involved hack that enables anyone to access hundreds of hidden levels in the original 'Super Mario Bros.' You need three items to pull it off — first up: an original 'Super Mario Bros.' cartridge: