The GB Hunter is an unofficial accessory that allowed you to play Game Boy games on a Nintendo 64. However, instead of being able to listen to the game's audio, you're instead treated to an obnoxious song that loops endlessly.
It could also function as a GameShark/Action Replay for Nintendo 64 games.
See if there's any way to display these in-game.
Present at 0x80015020 in memory is some build info.
RELEASE v1.1 GAME BOOSTER PAL Build 22.4.98 (SOUND FIX)
Present at 0x8001505C in memory is some text for a test mode.
N64 cart check PASS Flash program DONE Flash verify FAIL GB cart check PASS COMPLETE
In Europe, the GB Hunter is known as the Game Booster.
The Game Booster contains a built-in Game Boy game, Rebound Mission, that can be played by starting it up without a Game Boy cartridge plugged in. This game is not present in the GB Hunter.