Inside information on the Metroid series
According to Unseen64’s sources, Metroid Prime Hunters was originally pitched as a single-player game similar to Metroid Prime. It eventually became multiplayer focused and many of the multiplayer assets ended up being used to “make a mediocre single-player at the last minute,” according to a source at Nintendo Software Technology.
The long-lost 2D Metroid Dread reportedly looked like a port of the Game Boy Advance title Metroid Fusion, according to first-party developers who saw it behind closed doors at a pre-E3 event in 2009. The game went missing-in-action thereafter with no real specific reasoning as to why.