After you defeat the third boss (the one with the steam rollers and metal razor sharp teeth) your will be extra health and an extra high bounce where you use Rodney friend as a trampoline!
Defeating Ratchet's robots
When you get to Ratchet's huge robots with big blue eyes, try to destroy as many of them as you can. Wait until one of the robots' eyes open up and turn blue. Shoot the blue eye before it closes back up with one shot. The next part is much more difficult. You must battle Ratchet on top of his machines. Be careful -- he can do three moves: order his robots to attack you, throw a bomb at you (which you can shoot to destroy), and jump from one robot to another. When he stops on a robot, shoot him quickly. Do this process a few more times and he will be defeated.
On the "Half-Pipe" thing when you are rolling around, you can fly over the holes in the side by going as fast as you can and jump over the side with the hole.
Rodney says jokes
When you destroy a bad robot, sometimes Rodney will say jokes.
Rivet Town: Rodney's dad gives scrap
On the first level, after you have grown up, go to where Rodney's dad is located. Once you are in the diner in the room where he is found, he asks you to select the Scrap Launcher. Select it, but do not shoot targets yet. Instead, shoot everywhere else, but not at the targets. Use up all your scrap, and Rodney's dad will give you 10 extra scrap.