How can I unlock all the characters in Transformers for the Xbox 360?

I had all the characters in the game buy my son saved over the file. Now I have a 4 year old going crazy cuase he can't be Optimus Prime. How can I get the characters without playing through the game again?How can I unlock all the characters in Transformers for the Xbox 360?There is no way to unlock all the characters at once but here is a cheat to play as prime



Enter the following codes at the Campaign / Bonus Features / Credits menu

[Down], [Down], [Up], [Up], [Right], [Right], [Right]: Unlock Robovision Optimus Prime



[Down], [Right], [Left], [Up], [Down], [Down], [Left]: Play as Optimus Prime Generation 1 version