Unlike other Pokémon in the series, Gengar originally appeared in the manga Capsule Monsters, an early concept by Satoshi Tajiri which evolved into the basis for the modern Pokémon franchise. During development of Pocket Monsters games Red and Green, which were localized outside Japan as Pokémon Red and Blue, Game Freak illustrator Ken Sugimori adapted the character concept for the games. Called "Gengaa" in Japanese, Nintendo decided to give the various Pokémon species "clever and descriptive names" related to their appearance or features when translating the game for western audiences as a means to make the characters more relatable to American children. Originally intending to call the species "Phantom", due to an existing trademark for a character with the same name they adapted its Japanese name for the English language instead. It was given a "Mega Evolution" in Pokémon X and Y. Series producer Junichi Masuda noted that Mega Gengar was difficult to render in 3D due to some of the things it was going to do.