Press [Enter] at the main menu to display the "Secret Mode:" prompt. 
Then, enter one of the following codes to activate the cheat function. 
Note: Some codes will be permanently saved.

Result                           Code
-------------------------------------
Insane bonus level             - z rules
Insane II bonus level          - z really rules
Faith level                    - chastity
Time Machine mode              - mcfly
Invincible Bonus mode          - stalin
Unlock all bonuses             - malcom x
Insane bonus level             - insane
Insane II bonus level          - z is insane
Faith level in Time Quest mode - faith
Debug mode                     - bonnie and clyde
Disable non-permanent cheats   - reset d
Level skip                     - einstein
Start with 1 bonus             - zack
Start with 2 bonuses           - nostradamus
Start with 3 bonuses           - davinci
Start with 4 bonuses           - jfk
Start with 5 bonuses           - bendis
Start with 6 bonuses           - copernic