Reverse/Rebirth Mode
     To  get  Reverse/Rebirth Mode where you play through the story as
Riku, simply beat the game once as Sora.

Reverse/Rebirth Mode: 
     Beat the game as Sora.

Theatre Mode
     Beat the game once to unlock Theatre Mode, an extra option on the
main menu wherein you may re-watch any cutscene in the game.

Theatre Mode: 
     Beat the game.

Secret Card in Sora's Story
     Beat  Sora's  story  and  unlock reverse/rebirth mode. Go back to
Sora's story and the Ansem card will be in a chest in Castle Oblivion.

Roxas Card
     Roxas  card  (Doubles  attack  strength):  Go to Twilight Town in
Sora's  mode  and  enter the treasure room. There should be two chests
with one of them containing the Roxas card.


Special Cards

Ansem: 
     Beat Reverse/Rebirth mode and obtain from a chest in Castle Oblivion.
     
Diamond Dust: 
    Beat Riku's story and obtain from a chest in Castle Oblivion.

Getting Mushu and Xigbar card: 
     Go to Hollow Bastion and use key of rewards and there will be 
     two chests one containing Xigbar.

Lexaeus: 
     Beat Reverse/Rebirth mode and obtain from a chest in Castle Oblivion.

One Winged Angel: 
     Beat Riku's story and obtain from a chest in Twilight Town.

Roxas card (Doubles attack strength): 
     Go to Twilight Town in Sora's mode and enter the treasure room. 
     There should be two chests with one of them containing the Roxas card.

Ultima: 
     Beat Riku's story and obtain from a chest/shop in Castle Oblivion.

Zexion's Card: 
     Beat Riku's story and retrieve from a chest in Destiny Islands.