At the main menu, select the "Cheat Codes" option. Then, enter one of the 
following codes to activate the corresponding cheat function:

  Play as G1 Starscream 
  Enter Circle, X, Circle, R1, Triangle, R1 as a code to unlock G1 Starscream.
  Play as Gold Optimus Prime in Multiplayer mode 
  Enter Up, Down, Left(2), Right, Down as a code to unlock Gold Optimus Prime in 
  Multiplayer mode.
  Play as Gold Megatron in Multiplayer mode 
  Enter Down, Up, Right(2), Left, Up as a code to unlock Gold Megatron in 
  Multiplayer mode.