Pokémon Gray is a cancelled expansion to Pokémon Black & White that was planned during development, however was cancelled during development and was later reworked into Black & White 2.
Nothing is known about the game itself apart from the game title being trademarked by Nintendo at the same time as Black & White, alongside the domain name "pokemongray.com" being hosted by Melbourne IT DBS, which was the same web hosting service used for the Black & White website.