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.