This copy of Tetris was bundled in with a couple of other games I bought. It has a sticker on the back with a few cheat codes. Anybody remember the GameGenie system? :
Pokémon Fire Red: Cheats, Codes, and Walkthroughs
User guide: Cheat codes · OpenEmu/OpenEmu Wiki · GitHub
The Most Used Pokemon Emerald Cheats [including GameShark]
Pokemon Emerald cheats: Full list of emerald gameshark cheat codes, how to use them, and more | 91mobiles.com
Amazon.com: GameShark for Game Boy Color & Game Boy Pocket : Video Games
GameShark Game Codes for GameBoy Advance and SP : Mad Catz : Free Download, Borrow, and Streaming : Internet Archive