Get 100 Population Instantly: Press X, Right, Right, Left, Up.
View ALL Units: Press X, L, R, R, L.
Skip Missions During gameplay press 'Start' and hold ALL four shoulder buttons and press X, Up, Up, Left, Right, Left. If you have entered the code correctly a message will appear on screen as confirmation. When you have confirmation quit your game and when you get debriefed press X to advance to the next mission.