Billing Displacement: Mickey's presence on the cover only serves to remind players of the Disney elements in the game, because aside from being playable in mission mode, he only appears in one short cutscene and doesn't even meet the hero.
Double Subverted. Although Christopher Lee came back to voice DiZ in this game after Corey Burton voiced him in Re:Chain of Memories, he was replaced again in the 1.5 HD Remix due to added scenes and to keep consistency between the voices.
Similar to the above, the 1.5 HD Remix extended Mickey's sole scene with Riku, but because Wayne Allwine passed away shortly after recording the original, Bret Iwan had to take over.
A beta version of the game from 2006 had a MP gauge, suggesting that Kingdom Hearts II's magic system was considered instead of the panel-based one in the final product. There is also a bar labeled "LM", likely a Limit meter that charged up before letting the player use a Limit Break instead of having it be dependent on how much HP the character has left.
Luxord's Mystery Gear weapon was originally meant to be dollar bills.