Area 51 Codes -

Shotgun:
Pause game play, then press Triangle, Square, Triangle, Left, R1 to start with a shotgun.

Invincibility:
Pause game play, the press X, Circle(2), Triangle, Circle, X.

Level skip:
Select "Arcade" at the main menu, then aim at the black border of the boxes with "Beginning" or "Warp Ahead" to begin farther into the game than normal.

Hint: Rebel Kronn warrior:
Shoot the first three S.T.A.A.R. team members and nothing else at the beginning of the game. After the first human is shot, you will not be harmed by any gun fire. After the third human is shot, you will transform into an alien in the main hallway of the first level. You will have infravision when playing as an alien, which allows targets to be more visible.

Hint: Baby Aliens:
When you enter the building from the helicopter, shoot the exit sign when you see a purple alien, then shoot the first three lights. This gives you the opportunity to shoot baby aliens before they form.

Hint: Chow Palace:
When you get to the point where you fight the two grenade throwing aliens, kill them and the game should give you enough time to destroy everything around them. There are yellow drums and ammo crates at this location. There is a single alien and about fifty power-ups inside Chow Palace .

Hint: Killing the launching opponents:
Whenever you encounter the types of opponents that launch things at you, shoot at their head. Whatever they are shooting at you will also be hit, as if they were targeted. Just keep aiming at their head and they will eventually be killed. Note: This will only work on one person at a time.

Hint: Shotgun:
When you are in the warp ahead level, get up to the part where it says "Self Destruct". You will turn, a blue blinking light will appear. Shoot it and you will get a shotgun.

Whenever you receive a shotgun power-up you can simply aim in the area around the target to hit them. You do not have to aim exactly on target.

Hint: Easier game:
At the start of the game, select "Warp Ahead". This puts you much further in the game than the beginning. It may be harder, but playing the beginning tasks just wastes lives.