Cheat mode:
Enter "ROYGBIV" as a player name under the options menu to unlock all levels, mini-games, and hats. If you entered the code correctly, you will hear the sound of a foghorn.

Super Soviet Missile Master mini-game:
Successfully complete level 1-5 and the Super Soviet Missile Master mini-game will be unlocked after the intermission sequence.

Bonus life:
Dig next to a flower to get an extra life.

Indestructible bus in Level 1-2:
You will be brought into the level on a bus. You will then get out and the two cars surrounding the bus have the triangle button pointing to them to climb in; however they do not point to the bus you rode in. If you get into that bus it is practically indestructible. It also destroys other cars in one hit. Watch out for the helicopters dropping bombs; they are the only thing that can destroy the car.

Chicken hat in Level 1-4:
Destroy the Benemoth building. You should hear a foghorn sound to indicate that the hat has been unlocked.

Curly hair in Level 1-4:
Destroy the "Fish Are Like Plants" building. You will hear a foghorn sound once the building is destroyed, and the curly hair will be unlocked.

Desert trap in Level 3-2:
There is a flower in the sand; however, if you try to dig down to get it, a big green thing will eat you before you can take it.

Extra lives in Level 3-4:
After fighting the Boss (giant green robot with the eye and a fork and knife) and his life reaches zero, he will start exploding. Continue shooting at his eye. He will just continue exploding as long as you shoot, and you will continue gaining points. You can stop when you have about 60,000 points. At the end of the level, you will gain about seventeen lives.

Hats:
Go into the options menu and enter one of the following names as a player name. Select "Submit", and you will hear the sound of a foghorn if you entered the code correctly. Go into the hat menu and the corresponding hat will be unlocked:

Hat Name
2 (Tom Fulp) TomFulp
4 (Blonde hair) Cletus
5 (Red hair) April
7 (Jheri curl) Superfly
8 (Pirate bandana) Goodman
11 (Top hat) Grrl
12 (Diamond tiara) Abe
13 (Daisy headdress) Princess or Betty
14 (Dick Tracy hat) Dandy
(Rooster) Behemoth