In-game reset:
Hold R1 + L1 + Start + Select + R2 + L2 during game play.
Alternate ending sequence:
Successfully complete the game with all Keyholes locked
(including The Book Of Pooh), 99 Dalmatians rescued, and
the Hades Cup won.
Successfully complete the game under the expert difficulty
setting and view the secret trailer. A different screen
will appear at the end.
Hidden trailer:
Wait until the credits complete to view an epilogue of what
happens to Sora, Donald, and Goofy after the worlds come back.
It seems to be a teaser for another Kingdom Hearts game.
After that, there is a "Special Secret" which seems to be
a hidden trailer for yet another Kingdom Hearts game,
although this one seems to be about Riku and what happens
after the defeat of Ansem and the Heartless.
Note: The hidden trailer after the one with Pluto and the
letter is actually a portion of the trailer from Kingdom Hearts 2.
The Japanese game Kingdom Hearts Final Mix should show half
of that trailer.
Select Opponent option:
When you defeat Sephiroth, a new option (Select Opponent) in
Hades Cup will open. This lets you select an opponent to
fight with a lot of experience points.
Expert mode:
At the beginning of the game when asked to choose the difficulty
setting, select "Difficult" .When you are in the room with the
sword, staff, and shield, choose the sword. This is considered
expert mode. At the end of the game, you will get to see your
overall statistics and some artwork
Sites: