Unlock Secret Popup Duel Cards
Go to "Present" and select the "Popup Duel Present" option. Then enter the following codes to access hidden cards:
[Left], [Y], [Up], [R], [Left], [X] - Omega Card "Rocket Punch".
[B], [Up], [L], [X], [Y], [Right] - Madora Dark Card "Mist Grass".
[A], [L], [B], [A], [Down], [R] - Ragnarok Card "Sword of Destruction".
[X], [A], [Y], [Left], [Up], [Y] - Chocobo Card "Hip Attack".
[R], [A], [R], [Right], [X], [Up] - Shinryu Card "Cruel Angel".
[Y], [X], [Down], [B], [R], [A] - Ultima Weapon Card "Shadow Flare".