Enter GFJH as a password to unlock the hidden level skip feature; note that the game will inform you that your password is incorrect, but this won't be an issue during the game itself. Pause the game during any level and press A twice on the Surrender option (White Flag) to skip to the next level.
Press Up, Right 2x, Down 3x, Left 4x, A, Up, B, Down, C, Left, Down, Start at the title screen. Begin game play and use your men to fire three times. Your trooper will spin and disappear. A new laser-equipped trooper named Guido will appear. The laser has the ability to easily destroy most objects. Tanks and other defended targets will require more than one hit though.
Enter these on the load screen
Level 1 PXJND
Levels 1-9 have the same passwords as the NTSC version.