By changing the first and last names of a soldier via the customize menu, you can unlock one of 4 characters based off of the crew who made the game. Using them WILL disable trophies for that game, and make the earlier missions extremely unbalanced in your favor, as each soldier will have later game advanced armor and weapons, high stats and be at Colonel rank. Please note that loading a save game with any of these characters still disables trophies.

Effect	Password
Unlocks Joe Kelly - Heavy	Change name to Joe Kelly
Unlocks Ken Levine - Sniper	Change name to Ken Levine
Unlocks Otto Zander - Assault	Change name to Otto Zander