Things You'll Need
Instructions
Search the Internet for video game cheat websites with Wild Pokemon Modifier codes. Look for codes for the specific version of Pokemon you're playing. Codes built for one version may not work on another.
Look for two x's or variables mixed in with the line of letters and numbers that make up your code. You will need to replace these x's with the hex value of the Pokemon you want to capture. Most websites that host Wild Pokemon Modifier codes usually include a list of which hex value corresponds to which Pokemon. Look up your Pokemon and plug in the hex value. If you don't find a list of hex values, many websites dedicated to Pokemon host hex value tables.
Turn on your Game Boy with the GameShark and game plugged in. Scroll through the options on the GameShark menu until you find an option that is labeled "Enter code" or "new cheat." Depending on which version of GameShark you have, you may have to find the entry for the specific game you're playing on the menu before you can access this option. Once you've found it, enter the wild Pokemon modifier code and replace the x's with the appropriate hex value.
Check that the GS switch is in the off position and then load the game.
Find a patch of tall grass within the game and turn on the GS switch. Any patch of grass will do, as long as any wild Pokemon normally appear there. Walk around in the grass until you encounter a wild Pokemon. This should be the Pokemon you want. In older versions of Pokemon, such as the ones on the Game Boy and Game Boy Color, sometimes when you encounter your Pokemon it may have a scrambled or "glitched" game sprite and may not look like or have the correct name as the one you want. Don't be alarmed. Capturing this Pokemon won't harm your game or save file. Once you capture the Pokemon, it will become the one you want. Just save once you've captured it and turn off the GS switch. If it still has the name of a different Pokemon, you can take it to the name rater within the game and have him change the name for you.