It doesn't really have that many worlds, just the ability to have that many worlds. What's happening is that you're making it read various memory locations not normally used for the world pointer data. The game engine still loads whatever is there and can usually make a level out of the data it finds. However, these were not put there directly. I remember accessing some of these "worlds" with a Game Genie over a decade ago and at least one level had a Paratroopa that would change color when you stomped on it. Of course, if you made an IPS then likely some of the data that it is reading has changed.
