For all the codes below to work, you must start a new game and enter your name as "ICHEAT".
Fat Legs- Press Left, A, Right, Down. This makes aliens' legs bigger. Aliens must be present for this to work.
Mutant Cheat- Press C-Down, Up, Z, Z, C-Right, Right. If a harvester is present, this code will turn it instantly it into a mutant.
Mega Weapons- Press C-Down, C-Up, Up, Z, Z, Left, C-Right. This increases your weapon damage.
Surreal- Press C-Down, Up, Right, Right, C-Right, A, Left. Makes the buildings bounce, and hard to enter.
Weapons Cheat- Press A, Right, C-Down, C-Right, C-Up, A, Left. Gives you all available weapons for that stage.