Mario Golf for the Nintendo 64 has the ability to link and exchange data with Game Boy Color version of the same game. With the use of the Nintendo 64 Transfer Pak, the player can transfer the characters: Joe, Sherry, Azalea, and Kid from the GBC version to play through the Nintendo 64 version of Mario Golf (Source: https://www.mariowiki.com/Mario_Golf_(Nintendo_64)

This hack unlocks those 4 exclusive characters without requiring transfers with the Game Boy Color game.

The author found most of the necessary memory addresses in a massive list of GameShark codes compiled by Fancy. Without it this hack would not have been possible.