Continue Game Play
Press A, B, B, A at the Game Over Screen after losing during one of the first three levels of the game.

Level Select
Quickly press Up, Down, A, A, B, Left, Right, A, B, Up, A, Down, Right, Right, Left, B, Up, Left, A, Right, B, Left, Right, A, Left, Up, A, Down, A, Right, Left, A, Start at the Title
Screen. The phrase “Stage 1” will appear next to the airplane landing screen to confirm correct code entry. Press A or B to change the starting level.

Double Tank
Position both players on a tank and press A on both controllers.

Double Helicopter
Position both players on a helicopter and press A + B on both controllers.