Collect all 100 Gold Cards and beat Altair again to access a completely new world (Rainbow Palace).
First beat the game with 100 Gold Cards, then finish the extra world by defeating Sirius. If you now go to the Options menu, you can view the credits without having to beat the game again.
Beat the game in Adventure Mode (normal difficulty) and you will be able to access a sound test option.
Secret Battle Stages
Looking for more variety in your multiplayer battles? Go to the game selection screen (where you choose between adventure mode, battle mode, etc.). If you have a controller with a pause button press it, or just press the start button quickly and repeatedly until you hear a chime. You need to tap it quickly, as if you were playing a track-and-field game. Now go into battle mode and the four extra battle levels (In the Gutter, Sea Sick, Blizzard Battle, Lost at Sea) will be enabled. We have tested this code with BOTH the US and Japanese version and we assure you it works.
Secret Battle Levels (Import Version)
If you have the import version of Hudson's Bomberman 64, you can find some cool hidden battle levels. You need the Hudson JoyCard 64 controller for this to work. Go to the title screen, put the "Slow Switch" on position Hu and wait five seconds. You should now hear a sound that confirms that the trick worked. Choose Battle Mode and you can access four new secret stages