Keitai Denjū Telefang

Keitai Denjū Telefang (Japanese: 携帯電獣テレファング, Hepburn: Keitai Denjū Terefangu, lit. "Mobile Phone Beast Telefang") is a series of role-playing video games (RPGs) developed by Natsume and published by Smilesoft. In the games, the player contacts various creatures using a mobile phone-like device in order to get them to battle the foes he or she will encounter. Released exclusively in Japan on November 3, 2000, the first game in the series was released for the Game Boy Color in two versions: Power Version (パワーバージョン, Pawā Bājon) and Speed Version (スピードバージョン, Supīdo Bājon). Each version features several exclusive creatures. The name of the series derives from keitai (携帯), the Japanese term for mobile phone, as making phone calls to the creatures is an integral part of the games, and fang, to symbolize the various beasts involved.

On April 26, 2002, a lesser-known sequel for the Game Boy Advance called Keitai Denjū Telefang 2 (携帯電獣テレファング２, Keitai Denjū Terefangu Tsū, lit. "Mobile Phone Beast Telefang Two") was released exclusively in Japan. Likewise, two versions were released, also called Power Version (パワーバージョン, Pawā Bājon) and Speed Version (スピードバージョン, Supīdo Bājon), featuring similar differences in between them.

The game was never released in English, and is best known among English audiences for the bootlegged versions, Pokémon Diamond and Jade, which were hacked and sold as fake Pokémon games.