X-Men 2: Clone Wars

Pause the game.then press Down + C, Up, Left, Up, Right, Right, C.

First, you need to be on the very last stage of the game (the one with the big scorpion thingy that keeps on trying to flame-broil you). Make sure on this stage that you are not Magneto, or this code won't work. After the scorpion thing explodes, you have to face the X-Men clones. Here's where you have to be careful. You have to face your own exact clone(s) and you have to make sure you haven't destroyed all the clones. When you destroy your matching clone, go as far downward in the stage as you can to where the scorpion's legs turn into clones. Now go to the wall on the left side and hit it. You should get a smiley-face exploding on the screen. From there, take the right (not left) side of "rooms" and go into the "room" that is up two "floors" from where you were. Now go as far right as you can until you reach a small wall. Hit it! and enjoy seeing the power of Magneto's clone! After that you can beat the game.

What you need to do is defeat all the Phalanx X-Men clones except for one. It doesn\'t matter what order you do it in just so long as all but one are dead. Now, once you\'ve done that, head back down to the very bottom of the area -- the end of the hallway where the Phalanx mech\'s claws turned into your character(s). Now, hit the wall to the left. If you do this, the wall should emit a circle of explosions which circle around twice and into a sort of close-eyed blank-looking smiley face.(Looks like this -> -_-) Now, head back up into the second room from the bottom on the right. This room should have a wall blocking your progression. However, if you did as I said, if you hit this small wall, it should shatter like glass. Walk into the room, and there, you will fight Phalanx-Magneto!
Note: This does not effect the ending. It is just a nifty little bonus for those of you who like to explore.

Pause the game. Press Up + B, Up, Right, Down, Up, Right, Down, Down, Up, B. If done correctly, you'll hear a crashing sound. Unpause the game, then pause it again and press Up + B to activate the cheat.

Note: This cheat does not last the entire game. If your health begins to deplete, pause the game and press Up + B to reactivate the code.