Kaseki Sousei Reborn II: Monster Digger

Kaseki Sousei Reborn II: Monster Digger
Developer: Starfish Publisher: Starfish Platforms: Game Boy, Game Boy Color Released in JP: February 12, 1999 This game has debugging material. This game has a hidden sound test.

Debug Menu

At the title screen, press Select, Up, Down, B, Left, Start. The menu is identical to the first game's, containing music and sound effect tests, an intro/credits viewer, and a toggle that enables a pause cheat during gameplay (hold Select and press Start to pause, press Select to unpause).

(Source: Original TCRF research)