Activate the following cheats by entering the corresponding codes at "Main Menu" > "Options" > "Cheat Codes".

CHEAT FUNCTION - CHEAT CODE
John Cena's alternate costume - CENATION
Randy Orton's alternate costume - ViperRKO
Santino Marella's alternate costume - Milan Miracle
Shawn Michael's alternate costume - BowDown
The Dirt Sheet and Mr. McMahon's Office - BonusBrawl
The Rock - The Great One
Triple H's alternate costume - SuckIT!