Here's why:
* Generation Compatibility: Pokémon Gold and Crystal are from the second generation of games (Gen II), while Pokémon Red, Blue, and Yellow are from the first generation (Gen I). While they share some Pokémon, the games have different data structures, meaning they can't communicate with each other for trading.
To Trade between Gold/Crystal and Red/Blue/Yellow:
You need a special device called a Game Boy Transfer Pak. This accessory allows you to transfer Pokémon from Gen I to Gen II, but not the other way around.
Here's how it works:
1. Game Boy Transfer Pak: You connect the Transfer Pak to your Game Boy Color.
2. Insert Gen I Cartridge: Insert your Pokémon Red, Blue, or Yellow cartridge into the Transfer Pak.
3. Transfer Pokémon: You can then select Pokémon to transfer to your Pokémon Gold or Crystal game.
Important Note:
* Pokémon Transfer is One-Way: You can only transfer Pokémon from Gen I games to Gen II games, not the other way around.
* No Trading: The Transfer Pak is only for transferring Pokémon, not trading them.
Let me know if you have any other questions!