Unlock everything:
At the main menu, hold L1 then press 
Right, Right, Left, Left, Down, Up, Circle. 

Bonus characters and costumes:
Beat arcade mode using the following characters 
to unlock bonus characters and costumes:

Character To Use:      Unlock Character: 
Gambit                 Bishop 
Bishop                 Blob 
Phoenix                Dark Phoenix 
Betsy                  Psylocke 
Any Mutant Third       Costumes 

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