Which programmer secretly added Mew to the original Pokémon games?

Shigeki Morimoto secretly added Mew to the original Pokémon games. He programmed the Mythical Pokémon near the end of development, after debugging features had been removed and a small amount of space became available.

Mew was not intended to be obtainable through normal gameplay. Morimoto added it as a secret known to Game Freak staff, helping create the rumors and mystery that surrounded the early games.

Satoshi Tajiri had conceived the idea of an elusive, phantom-like Pokémon, but Morimoto handled the in-game addition and designed its original sprite. Ken Sugimori later produced official artwork based on the sprite.

Mew was numbered 151 in the original Pokédex, after the first 150 species. Its hidden presence helped fuel interest in Pokémon Red and Green before official distributions made Mew available to selected players.