Cheat mode
Enter the following codes in the Enter Cheat Menu for the desired effect.

Code - Result:

DGHTTSRS - All Keys
NGLCKCK - All Keys
MGRLSGTM - All Weapons
THMSCLS - All Weapons
PRMSHN - Big Heads
BGGNTSS - Disco Mode
KNTSFSKS - Fly Mode
BKSTRD - Fly Mode
TRNTNNQ - Full Map
HTSDNM - Gallery Mode
JFFSPNGDNBRG - Infinite Lives
LLSNMRTN - Invincibility
DDDNSTBR - Invincibility
CRLSFNDNGS - Purdy Colors
GSRCGKFS - Quack Mode
LRNMSNHR - Show Credits
TKMDKK - Show Enemies
MBRNKLSN - Spirit Mode
NDNLP - Spirit Mode
HFLLTHSH - Tiny Enemy
RHNSRLL - Unlimited Ammo
LNJHNSN - Unlimited Ammo

Level Password Variations
Enter these level password at the cheat menu if the others do not work.

Code - Result:

HSTSMN - Campaigner Boss
PTLFGNDS - Level 1
QTMBGS - Level 2
GTMNDSBF - Level 3
NCPGHM - Level 4
RSTPDFRPL - Level 5
BGRSD - Level 6
NBCD - Level 7
LFRRSPR - Level 8
CRCDND - Longhunter Boss
CTNTSCND - Mantis Boss
THSFNDNT - T-Rex Boss

Level Passwords
Enter these passwords in the Enter Cheat Menu.

Code - Level:

MTTSTBBNGTNB - Level 1
DRRNSTBBNGTN - Level 2
MKJNK - Level 3
PTNDNCN - Level 4
NNTND - Level 5
TRMNN - Level 6
JMDNN - Level 7
MRGRTTRR - Level 8