Things You'll Need
Instructions
Plug the Game Genie into the top of your Game Boy Color by sliding it into the game slot. Slide Pokemon Gold Version into the slot on the Game Genie with the label on the cartridge facing inward.
Power on the Game Boy Color and head to the code entry screen after the Game Genie software loads.
Enter the code "971-38B-910."
Start Pokemon Gold Version. Select "New Game" from the main menu.
Go through the normal process of starting a new game, which involves setting the time, date, your name and your rival's name.
Head downstairs once the game starts. Exit the house and go to the building immediately to the left, Professor Elm's lab.
Choose the middle Poké Ball when prompted to choose a starter Pokémon. Totodile's image will appear on the screen but choose it anyway. Check your party and you should have the legendary Pokémon Mew.