Press R1, Circle, R1, Square, Left(2), Right, Left at the difficulty selection screen.
All Mini-Cons
While playing, pause the game and enter R2, R1, LEFT, RIGHT, LEFT, RIGHT, CIRCLE, SQUARE.
Big Head Mode
Press Circle, Circle, Circle, Square, L1, L1, L1, L2 at the difficulty selection screen.
Deep Amazon Level Completed
Press Left, Right, Left(2), Right, R1, R2, Circle at the difficulty selection screen.
Earth Level Completed
Press R2, R1, L1, L2, Square, Circle, Square, Circle at the difficulty selection screen.
Extra Cinema
Collect all of the mini-cons to unlock an extra cinema.
Fight Unicron
First you need to beat the Pacific islands level, then you need to have gotten a total of 30 minicons. When you do these two things you can go to the Cybertron level where you fight Unicron in his planet mode.
Mid Atlantic Level Completed
Press Circle, Square, Circle, Square, Right, Left(2), Right at the difficulty selection screen.
One Hit Kills
While playing, pause the game and press SQUARE, CIRCLE, SQUARE, CIRCLE, L1, L1, L2, L1. You will hear "Code Accepted" when entered correctly.
Starship Level Completed
Press Left(2), Right, Circle(2), Right(2), Left at the difficulty selection screen.
Turbo Mode
Press L1, R2, R2, Square, Square, Square, Square, L1 at the difficulty selection screen.