Hit ESC and type a cheatcode:

Code - Result

IAINTSCARED - God Mode
SHOWMETHEMAZES - All Levels
INEEDTHEPOINTS - Win Level
INEEDANEXIT - Win Level
HONEYISHRUNKPACMAN - Shrink PacMan
HONEYIBLEWUPPACMAN - Blow Up PacMan
UPCLOSEANDPERSONA - First Person View
BEINGPACMANOVICH - First Person View
GETALIFE - Add 1 Life
KILLME - Kill Yourself
PACSTATS - FPS and Other Stats