In the very first Japanese release of the original game, at the bottom of the well in Corel Prison, a rare debug enemy known as "Test 0" that was accidentally left in the game on its initial release can be randomly encountered. This encounter does not require cheats or hacks to occur, although GameShark codes can be used to access every other debug enemy battle in the game. This battle was removed from all future releases of the game. "The Completely Unauthorized Final Fantasy VII Ultimate Guide" by Versus Books, released in 1997, features an entry on this enemy (note that the HP listing in the guide scan is incorrect; Test 0 has 30000 HP).

Final Fantasy VII Rebirth nods back to this oversight by making Test 0 a legitimate optional encounter in the Beast Battleground. The nature of its presence in the original game is referenced in the enemy's bestiary entry, which describes it as "A test subject that managed to escape Shinra's R&D Division due to a developer's oversight."