Fighting the Zombiebot King
In order to beat the Zombiebot King just wear him down using rockets until he pauses (doesn't move). Toss a grenade (coring charge) into its mouth. On Normal, it takes five grenades to kill him and after the 3rd and 4th grenades there are regular zombiebots that swarm the arena.
In any multi-player level, press Start. You can be shot at, but receive no damage. You cannot move, but it is better than dying.
Original Concept FMV sequence
Successfully complete the game in campaign mode.
Multi-player General Corrosive
Successfully complete the game with all secret and speed chips to unlock General Corrosive as a playable character in multi-player mode.
Getting Past General Corrosive
When playing in the coliseum, you will fight against General Corrosive in the last match. You cannot hurt him. When you enter the arena, run to the far right side. There is a box that has a health in it. Hide on the side opposite General Corrosive and get him to destroy it with a rocket. When he does, get the health. There is also a wrench when you get the health. Run from the general and hide in one of the small huts. When inside, quickly disassemble yourself. The general will destroy the hut and find you in pieces. A short intermission sequence will play and you will proceed to the next level.
Cleaner in level 15 Minutes
In the level 15 minutes, the old droid in the jail cell will talk to you, when the mils come to get you, hit them with you're arm until they start shooting at you, when they do this hide behind the old droid and the mils will destroy him instead of you and a cleaner should appear! Now use it against those Titans.
Completing Final Battle
To kill corrosive without getting hurt, hide under the curved tunnel just in the entrance looking out towards the right hand wall of the arena, and he will position himself a few meters in front of you. You can then shoot everything you have at the hole in the red patch in his armor while he does absolutely nothing to defend himself.