Destroy All Humans! [PSX]
Hold L2, enter cheat, then release L2.
Square, circle, left of d-pad, left on d-pad, circle, square
left on d-pad, circle, R2, right on d-pad, R1, square
R1, R2, circle, right on d-pad, R2, circle
Faster Destruction In The Ufo
Instead of holding R to destroy buildings or large objects, tap R1 and the destruction will happen faster without waiting for the recharge.
Finding More Probes
Probes are necessary to get upgrades faster. In order to find them all, make sure to look high up on rocks or hard to reach places. Your jetpack is essential in getting to the high places. You may have to get up on the ledge or building, then use your jetpack to fly higher to get the probe.
Getting Away From The Law
Forget running away from the authorities with short legs. Use your jetpack liberally to fly away. Press Left Analog-stick Forward and hold X to boost away.
Put your target (dot in the middle of the screen) on any human, and press Circle. In order to maintain your HoloBob, you must read the thoughts of the humans walking around. You can read the same person's thoughts repeatedly to keep your mental powers charged.
Stand in an open area on any level and walk forward. Keep decreasing your speed until you eventually begin walking in place.
Allow the game to idle. Eventually the screen will turn black and white and elevator music will play in the background.
Pause game play, then hold L2 and press Square, Circle, Left(2), Circle, Square while on the Mothership. All upgrades for the currently unlocked weapons will be available for purchase from Pox's lab.
Better DNA value
Every chance you get, do not kill the human before you extract their brain stem. Extract their brain stem first as it will make the DNA worth more (25 instead of 10).The easiest humans to do this to are the scientists in the level with glowing cows. For some reason, if the person that is important to you dies (the person you need to abduct), extract their brain stem before you return to the Mothership -- the DNA is usually worth more.