Pokemon #151, Mew, is a member of an original breed of concepts and ideas in early games that are often referred to as mysteries. With Pokemon HeartGold and SoulSilver releasing just yesterday, Iwata of Nintendo sat down with Tsunekazu Ishihara-san, President and CEO of The Pokémon Company, and Shigeki Morimoto-san of Game Freak to discuss some of the more interesting topics from the forever growing Pokemon series.

Back in the day when Pokemon Red and Blue had just released in the United States, Mew was a rumor amongst children on the playground. Some players claimed to have seen this elusive Pokemon, while others disputed it with certainty. We now know that Mew had always been in the games code, but had been hidden away from the public.

Mew was originally imagined as a result of 300 bytes of free space on the game cartridge. At the very end of development, when the debug features were removed from the game, a very small amount of data was left unused. Doing the unthinkable, and after being specifically told not to tamper with the game after the debug process, members of the team decided to add Mew into the game anyway, which had the possibility of unraveling the entire process of debugging in the first place.

The original plan for Mew from it’s creators was for the Pokemon never to make an appearance in game unless a good opportunity revealed itself. It’s possible that, even today, Mew would have never been revealed. However, thanks to a small bug in a select few of the shipped games, Mew appeared.

After the news of Mew spread, Nintendo arranged for CoroCoro Comic’s to hold a “Legendary Pokémon Offer” where 78,000 players signed up to send their game cartridges into Nintendo to have Mew uploaded to their file. Out of the 78,000 entrants, only twenty winners were selected.

Many employees at Nintendo believe Mew is the reason Pokémon is so popular today. After these events surrounding it had been revealed, the sales of Pokémon Red and Blue exploded.

The entire “Iwata Asks” can be read here, Pokémon HeartGold and SoulSilver are now on sale.

Iwata Asks Pokémon HeartGold Version & SoulSilver Version [Nintendo]