-Rescue the other two players and complete the game. The phrase "You've got the special key" will appear after the credits. Save the game. Start the game that was just saved. Enter the room with the big mirror on the second floor of the mansion. Unlock the door in the back. Enter the closet and move all the way to the end of the rack of clothes. A message asking "There is an outfit that fits you perfectly, do you want to put it on?" will appear. Select "Yes" to change your character's clothes.
-Play as Chris and acquire the Special Key. Open the door to the rack of clothes. When playing as Rebecca, you now can change your clothes there.