Ghostbusters II (Game Boy)

Ghostbusters II
Developer: HAL Laboratory Publishers: Activision (EU/US), HAL Laboratory (JP) Platform: Game Boy Released in JP: October 16, 1990 Released in US: December 1990 Released in EU: 1989 This game has a hidden sound test. This game has regional differences.

If there's something strange in your neighborhood, who are you gonna call? Probably 911.

Sound Test

The Japanese version of the game has a hidden sound test (with a visualization of the sound channels and tones being played) which was removed from the US / European release. To access it, lose the game. On the Continue screen, highlight "End" with the cursor, press and hold Select, then press B. Press Up or Down to change the selected sound, and press A to play it.

(Source: http://urawaza.in/gb/gostb2.htm)

Ending Test

You can also see the game ending in the Japanese version by losing a game, selecting "End" with the cursor, holding Select, and pressing A. The game will freeze after the ending finishes.

(Source: http://urawaza.in/gb/gostb2.htm)