Secret Worlds
From M2K2: Metroid Prime 2 Wiki
A Secret World is an area that you see when you exit a room from it's intended boundaries. This name was first from the original NES Metroid, and have been carried on in Metroid II: Return of Samus, Metroid Prime, and now, Metroid Prime 2: Echoes. The areas are usually glitchy, and can cause your game to lock up, thus having to restart. But, Secret Worlds have helped us in fact. In Metroid 2, they serve as a shortcut at times. In Metroid Prime, they served as a different way to understand the game, and even Sequence Breaking. Who knows what they will provide us with next!
That's all for now!
