Pokémon Box: Ruby & Sapphire

If you don't have space in your Pokémon Ruby and Sapphire, then put your Pokémon in Pokémon Box: Ruby and Sapphire. It is not a game; it just stores your Pokémon. There are limitations on this, though. You have to be the OT to withdraw Pokémon, or you MUST have 100 Pokémon registered in your Pokedex. This is a very efficient way to trade Pokémon without two GBAs. You can connect Ruby, Sapphire, Emerald, FireRed, or LeafGreen. If you connect the latter two, you cannot select 'Go to Adventure'.