Densetsu no Starfy for the Game Boy, and later for the Game Boy Color was a tentative Starfy title which was eventually canceled, though it was eventually released in the form of Densetsu no Starfy for the Game Boy Advance on September 6, 2002. Any initial plans of releasing Densetsu no Starfy for the Game Boy Color were abandoned in anticipation of the release of the Game Boy Advance.
A prototype of Tomato Adventure, while it was known as Gimmick Land and was on Game Boy Color (rather than Game Boy Advance) was discovered among the September 2020 lotcheck leaks.
Game Boy Bunko: Hajimari no Mori is a seemingly-never-announced port of Famicom Bunko: Hajimari no Mori which was discovered among the September 2020 lotcheck leaks.
Metroid II: Return of Samus DX is a rumored Game Boy Color port which was never released.
A screenshot was featured in the German gaming magazine "Club Nintendo" that was claimed to make use of the Game Boy Color's vast color-palette. However, the game never released and its existence has been contested by a testimony from Nintendo of America translator Dan Owsen who was unaware of plans for the port, suggesting that the screenshot featured in the magazine may be a mock-up.
Panel de Pon GB is a canceled game for the Game Boy Color. The game was mostly a port of Panel de Pon (SFC), but with a new story and some elements from the cancelled Panel de Pon 64, which later resurfaced via the Nintendo Puzzle Collection compilation for the Gamecube. The game was eventually cancelled and turned into Pokémon de PanePon. However, most of the game data still remains inside of the Pokémon de PanePon rom.
Pokémon Prism is a super customized Pokémon Crystal mod that takes place in a previously unexplored region. It contains new mechanics unseen in its inspired franchise, while refining existing gameplay.
Boasting an expansive landscape to adventure in filled with unique challenges, fresh areas to explore, and new ways to play, Pokémon Prism is an entirely new experience that gamers of all ages are sure to enjoy!
Pokémon Prism was planned to be released on December 25, 2016. It was cancelled several days prior to release, on December 21, following a cease and desist by Nintendo in which all the developer's ROM hacks were pulled offline, but later leaked onto the Internet.
Resident Evil was planned for a GameBoy Color adaptation in a project outsourced to British company HotGen Studios, Ltd. Intended for an Autumn 1999 release, it was repeatedly delayed due to programming issues, and ultimately cancelled in March 2000 in favour of M4, Ltd.'s alternate proposal for a new game made from the ground-up for the console, which became Resident Evil: Gaiden.
Developed by Russian R-Lab but development was halted early on. "This is our 3D shooter. Game was freezed on early stage of development, but we decided to release the engine for download."
This canceled Game Boy Color game was to be a prequel to Lufia II as it told of Maxim's early days as an adventurer years before the Sinistrals strike.