All Money:
If you fail to get all of the career money in a season just return to the stages that you didn't get all of the money in. Start the stage then hit pause and quit. You should have the full $1000.
All Bikes:
At the main menu press L2 + Square, L1 + Right, L2 + Circle, L1 + Left, Square.
All Riders:
At the main menu press Right, L1 + Right, Down, L1 + Left, Right, Square.
All Tracks:
At the main menu press Triangle, Right, L1 + R1, Square + Circle, L2 + Circle, Square.
Unlock Everything:
At the main menu press Triangle, L1 + Left, Square, Triangle, L1 + Right, R1 + Down, R1 + Right, SELECT.
Unlock New Bikes:
Unlock the following bikes by completing the challenges shown:
Custom Bee: World's Highest Jump Challenge
Custom Cow: Brave the Vertical Drop Challenge
Special Fire: Dominate 250cc Pro Freestyle Season Challenge
Special Tiger: Dominate 125cc Pro Freestyle Season.
Unlock New Track Editor Pieces:
Complete the action shown to unlock the piece:
Ramps: Impossible Wheelie Challenge
Movable Objects: Impossible Stoppie
Barriers: Dramatic Entrance
Station Z Arena/Floating Platforms: Cross Training.
Unlock New Riders:
Unlock the following riders by completing the challenges shown:
Cameron Steele:
World's Longest Jump Challenge.
Sal the Alien:
Find Out the Truth Challenge.
Elrod the Viking:
Lift Tower Challenge.
Superfly:
Crane's Eye View Challenge.