Pokemon Crystal also introduced a feature into the Pokémon series which wouldn't exist again until five years later with the advent of Pokémon Diamond and Pearl. At the same time Pokémon Crystal was released in Japan, a new peripheral was released called the Mobile Adapter GB. This Japan Only peripheral allowed you to connect your GameBoy Color up to your mobile phone, and use the mobile phone in order to make connections around the world.

Once you connect the Mobile Adapter to Pokémon Crystal, two new options will appear on the home screen, Mobile and Mobile Stadium. Mobile, which allows you to connect to it, unlocking the PCC and Battle Tower. Mobile also contains features such as the Name Card Folder which allows for you to track your friends, your own Profile and various other features. It also allowed you to battle in special Tournaments that were held that then you could check rankings of and save the battles. Mobile Stadium allowed for the connection with Pokémon Stadium 2 in order to view battles you have had in tournaments in full 3D.

The service has since ended, on December 18th 2002, so these features can no longer be used.