Pokémon Red and Green took six years to produce, according to Satoshi Tajiri's biography.
The games began as an ambitious Game Boy project inspired by Tajiri's childhood insect collecting and the communication possibilities of the Game Boy link cable. Instead of treating the link cable only as a competitive feature, Tajiri imagined players exchanging collectible creatures.
The extended development period placed heavy financial pressure on Game Freak. The company reportedly struggled to pay its employees, and investment from Creatures helped the project reach completion. Shigeru Miyamoto also mentored Tajiri during development, contributing guidance as the concept took shape.
The six-year figure refers to the production of the original Japanese games, not the time between the international releases or the later television anime. Pokémon Red and Green finally launched on February 27, 1996, after a long development process that helped define the franchise's collecting and trading identity.