Pokémon Blue Version, along with its sister game, Pokémon Red Version, were the first Pokémon video games released in North America. In Japan, Pocket Monsters: Green was previously released with Pocket Monsters: Red, while Pocket Monsters: Blue was released later on in Japan as a minor upgrade to both. The video games Pokémon Red Version and Pokémon Blue Version released in North America used the graphics along with the gameplay tweaks from Pocket Monsters: Blue, but maintained their exclusive Pokémon catches. The original Japanese Pocket Monsters: Green and Pocket Monsters: Red were basically the same, except for slightly different graphics.
Both games are exactly alike except that a handful of Pokémon are exclusive to each version. The two versions were designed to be bought by different people, who would then use Game Boy link cables to trade and battle their collected Pokémon. To emphasis the importance of trading, four Pokémon have to be traded in order to unlock their final evolved form.
The massive success of the game revitalized the Game Boy, and revived many returning franchises such as Monster Rancher and prompted Japan to port over new ones like Digimon. Many other games such as DemiKids and Mega Man Battle Network borrowed the "Two Version" format for their games as well.
When the series made its way to the Game Boy Advance, remakes of Red & Blue were published with better graphics, some new locations and updated features, and a few of the new Pokémon. These were Pokémon FireRed Version and Pokémon LeafGreen Version. The purpose of these remakes was to allow players to catch and trade the original 150 Pokémon and bring them into their new Game Boy Advance games, since the original Game Boy and Game Boy Color games were not compatible with the new link cable.
Japanese and English Versions
Pokémon Red Version and Pokémon Blue Version were the first Pokémon games to be released in North America, on September 30, 1998. The Japanese equivalents were Pocket Monsters Red and Pocket Monsters Green, released on February 27, 1996. However, the sprites for Pocket Monsters Red and 'Pocket Monsters Green were not used for the Pokémon Blue Version and Pokémon Red Version releases in the US. The Japanese Pocket Monsters Blue was the third Pokémon game released in Japan on October 10, 1996. It was released as a graphical upgrade from the original games, Pocket Monsters Red and Pocket Monsters Green, and was used as the engine for the American Pokémon Red Version and Pokémon Blue Version releases. In Pocket Monsters Blue version the Mew Glitch was removed, the catch rate was adjusted, and the Cerulean Cave is different from the Japanese Pocket Monsters Red and Pocket Monsters Green and was used for the US version of Pokémon Red Version and Pokémon Blue Version.
You are a young boy in a world where creatures called Pokémon exist in the wild. Their purpose is to be pets, or caught and trained for competitive battle. One day, your neighbour Professor Oak offers you one of three Pokémon: Charmander, Bulbasaur or Squirtle. Once you choose, Oak asks you to fill up his Pokédex by seeing and catching as many Pokémon as possible.
Oak's nephew Gary (Shigeru in Japan) is on the same mission. While you're filling up your Pokédex, you are also looking to become the Pokémon Champion by defeating every Gym Leader in your country of Kanto, then defeating the Elite Four in the Pokémon League.
There are 11 Pokémon which are only found in this version.
Mew cannot be obtained normally in-game; it had to be obtained at an Nintendo Promotional event, by using a GameShark or Codebreaker, or by using the Mew glitch.