To activate a cheat, press [Backspace] + P and enter its corresponding code below.

Cheat                              Code 
16 Color mode                      DDAPOGEE
All weapons, refill ammo           GUNHED
Bonus level                        DDHOOKER
Difficult enemies                  DDDOOM
Display message ("AWESOME")        DDTIM
Display message ("GREETZ")         DDGREETZ
Display message ("HAHAHA")         DDAJRAN
Invincibility                      DDBOUF
Level skip                         DDLAMER
Kill character                     DDMARK  
Quit to DOS                        DDKEN
System information                 DDCHECK
Teleport                           DDHOCUS
Toggle airboard                    DDSTRIKE
Toggle jumping                     DDSABLE
Toggle escort bird                 DDBAD

To view the ending sequence, press [F10] + [F11] + [F12] at the level select screen.