A recently surfaced documentary detailing the creation of 2007's Pokémon Diamond and Pokémon Pearl has provided a wealth of behind-the-scenes information for fans. The footage offers glimpses into the development process, including early designs for iconic Pokémon and ideas conceived two decades ago that may finally see implementation in upcoming titles.
During an analysis of the documentary, YouTuber and Pokémon archivist Lewtwo identified a segment containing numerous Pokémon designs on stacks of paper in the background. These designs were not the primary focus of the documentary and are obscured by low resolution and contrast. Lewtwo reportedly spent hours enhancing the footage to discern the details of these unreleased concepts.
Among these early designs was a concept for Gastrodon, a sea slug Pokémon known for its regional appearance variations. In Pokémon Diamond and Pearl, two versions of Gastrodon were implemented: a brown variant from the West Sea and a green variant from the East Sea. The fundamental concept for these regional differences was reportedly conceived by game director Junichi Masuda during the development of Pokémon Ruby and Sapphire, though it did not manifest until five years later with the introduction of Shellos, which evolves into Gastrodon.
The newly discovered design, however, depicts a yellow Gastrodon, a variant that has not yet appeared in any Pokémon game. This scrapped idea has found a new life in the lore of the cozy game Pokémon Pokopia, where researchers are noted to be searching for a yellow Shellos. It appears this narrative element was drawn directly from Game Freak's design archives.
Lewtwo described the rediscovery as a "mind-bendingly unbelievable full-circle moment for one of Sinnoh's fan favorite designs." While Shellos itself is not present in Pokémon Pokopia, the existence of this early design and its incorporation into new lore suggests a potential for its reappearance.
Rumors suggest that Pokémon Winds and Waves, slated for release on the Nintendo Switch 2 in 2027, will introduce approximately 300 new monsters, many of which are expected to be regional variants. The game is also set to feature 3D ocean exploration, a biome where sea slugs naturally occur. This confluence of factors makes the potential inclusion of the long-dormant yellow Gastrodon concept a distinct possibility for the upcoming title.