Creatures

Unlimited lives:
Wait until the high score screen appears after the title music stops.
Then, repeatedly tap  Left  Right on the  Joystick.
The sprites of Clyde will begin to jump.
Keep tapping the  Joystick  until they turn gray.
Then, begin game play for unlimited lives.
Alternatively approximately three or four minutes for the title screen music to stop playing.
Then, hold  [Ctrl]  +  2  when the high score screen appears until the sprites of Clyde turn gray.

Unlimited lives (main game):
Load or reset the game, then execute the following BASIC command before running or restarting the program.
POKE 7328,208

Unlimited lives (first torture screen):

Load or reset the game, then execute the following BASIC command before running or restarting the program.
POKE 33734,173

Unlimited lives (second torture screen):

Load or reset the game, then execute the following BASIC command before running or restarting the program.
POKE 33952,173

Unlimited lives (third torture screen):

Load or reset the game, then execute the following BASIC command before running or restarting the program.
POKE 33505,173

Invincibility:
Load or reset the game, then execute the following BASIC command before running or restarting the program.
POKE 15596,60

Unlimited shields:
Load or reset the game, then execute the following BASIC command before running or restarting the program.
POKE 44183,173