Upgrade all weapons:
To fully upgrade all your weapons, pause the game and press Up(2), Down(2), Left, Right, Left, Right, B, A, Start. Note – This code can only be entered once per level; repeating it will cause death. Also, you must have an upgradeable weapon or else you will die. This does not work on Easy difficulty.

99 lives:
To get 99 lives, lose a life at the exact same time you gain an extra life. To easily accomplish this, defeat the mini-Boss in Level 1 and you will get an extra life. Get hit by one of the fireballs it shoots immediately after destroying it.

Challenge mode:
To unlock Challenge mode, beat the game.

Challenge mode bonuses:
Unlock the following bonuses by completing the corresponding numbers of challenges:

NES Contra – 4
NES Super C – 8
Probotector character – 12
Nobuya Nakazato interview – 16
Lucia character – 20
Contra 3 comic – 24
Sheena Etranzi – 28
Jimbo and Sully from Contra 3 – The Alien Wars – 36
Sound Test option – 40

Alternate colors:
To play with an alternate color, beat the game. Then, at the character selection screen press Up or Down.

Alternate ending:
To view an alternate ending, beat the game on Normal or Hard.

30 lives in NES Contra:
To get 30 lives in NES Contra, before the demonstration begins at the Contra title screen, press Up(2), Down(2), Left, Right, Left, Right, Y, B, Start.

Hard mode in NES Contra:
Beat NES Contra to unlock the Hard difficulty setting for it.

10 lives in NES Super C:
To start with 10 lives in NES Super C, at the title screen, press Right, Left, Down, Up, B, Y.

Sound test in NES Super C:
To unlock the Sound test option in NES Super C, as the game’s logo is fading at the title screen, hold Y B and press Start.