IDDQD - Kills the player. Originally the Godmode cheat in Doom, it is a joke by the developers by making it have the opposite effect in This Game. When entered, on the screen is displayed: TRYING TO CHEAT, EH? NOW YOU DIE!
IDKFA - Removes all weapons and ammo the player is carrying. Any weapon that exists as a map item can be regained by picking one up, but the Golden Spaghetti will be lost for the remainder of the game session. It can, however, be recovered by using the All Weapons code. Just like the 'iddqd' cheat, this code is from Doom. In Doom, it gives all keys, armor and ammo. In This Game it does the opposite by taking them all away. The screen says: "CHEATER - YOU DON'T DESERVE WEAPONS"
IDSPISPOPD - Clipping (Mario can't walk through walls, monsters, and obstacles, climb high ledges instantly, and pass through items and across all tagged linedefs with no effect. Just like the 'iddqd' cheat, this code is from Doom. In Doom, it gives no clipping. In This Game it does the opposite by making Mario able to get hit by monsters. The screen says: TRYING TO CHEAT, EH? NOW YOU DIE!