Secret Battle Level
Enter 3636 as a password. You will then be taken to the screen where you choose between battle mode and maniac mode. Select battle mode and select your desired options. The new stages are Under the Sea, and Bomber Shock. Passwords - Japanese Version

Stage 1
Area 1 : 8010
Area 2 : 1180
Area 3 : 8086
Area 4 : 2919
Area 5 : 1021

Stage 2
Area 1 : 0127
Area 2 : 1220
Area 3 : 1018
Area 4 : 0804
Area 5 : 0714

Stage 3
Area 1 : 1027
Area 2 : 2413
Area 3 : 3009
Area 4 : 6502
Area 5 : 6809

Stage 4
Area 1 : 0627
Area 2 : 8808
Area 3 : 3674
Area 4 : 4891
Area 5 : 0605

Stage 5
Area 1 : 0730
Area 2 : 2151
Area 3 : 3562
Area 4 : 3812
Area 5 : 2203

Bonus Modes - Japanese Version
To play the bonus modes, enter one of these passwords.

Special VS Mode - 5656
Special Battle Mode - 4989
Battle Royal Mode - 1616
Maniac Mode - 4622

Best Equipment - Japanese Version
To start with the best equipment, enter one of these passwords.

Area 1 : 7327
Area 2 : 9717
Area 3 : 5211
Area 4 : 1814
Area 5 : 1029

Secret Battle Level
Enter 3636 as a password. You will then be taken to the screen where you choose between battle mode and maniac mode. Select battle mode and select your desired options. The new stages are Under the Sea, and Bomber Shock.

Two secret levels
Go to password and type in 3636. It will get you to 2 secret levels.