Rhythm Tengoku (Game Boy Advance)

Rhythm Tengoku is a Japan-only GBA rhythm game.

Space Dance
Using a tile viewer within an emulator, one can see unused sprites for the minigame "Space Dance." The player must turn right, sit down, or punch.

Tap Dance
As documented by Y.S., there are some unused graphics in the "Tap Trial" games. More information is available here and archived here.