PNTNNP     Mission 2
NGMLQP     Mission 3
SPLGZW     Mission 4
DQRFKW     Mission 5
PSQQLW     Mission 6
NBGJVX     Mission 7
VKPDMX     Mission 8
SDKNSX     Mission 9
PVBWGJ     Mission 10

Cheats

At the start screen, select, "Cheats". When on the cheats screen highlight "Enter Cheat". Below are the cheats to be entered:

GOLDENPIE  All Cheat
SKIPPY     Level Select
LOADED     All Weapons
SORTED     Infinite Ammunition
SKETCHY    Pen and Ink Mode
SONIC      Fast Run Mode

Multiplayer Codes 

LEGGY      Hive Guard in multi-player mode
RUBBER     Volcano Guard in multi-player mode
CLAW       Egypt Fodder in multi-player mode
UGLY       Hive Fodder in multi-player mode