Blooper: When Oogie Boogie is defeated the first time, his Brain Bug will not vanish behind Sora, and in fact will clip over him, during the Item Get!. This error appears in the PlayStation 3 and PlayStation 4 versions.
Contest Winner Cameo: Kurt Zisa, a Heartless Superboss present in the international and Final Mix versions, is named after the winner of the contest held in the USA two months prior to the game's North American release. The boss appears if you try to fly to the Cave of Wonders from Aladdin's house after visiting Hollow Bastion.
Cowboy BeBop at His Computer: Dan Birley, the author of the game's official strategy guide, stated that Sephiroth shouts an attack called "Sin Harvest". In actuality, the line is supposed to be "Descend, Heartless Angel" but the echoing voice and loud sound effects make it easy to mishear it.
Dawson Casting: Kathryn Beaumont, who provided the voice and physical model of Alice and Wendy as a child in the 1950s, reprised both roles in the game in her mid-sixties, and remarkably sounded almost no different. She's also one of only a few actors/actresses who worked with Walt Disney directly to be involved with the Kingdom Hearts games as well; John Fiedler, who voiced Piglet, did the role in the games as well until his death.
Rikku from Final Fantasy X was going to make an appearance as part of the Final Fantasy gang in Traverse Town, but she was replaced with Yuffie. As a nod to this, Yuffie wears an outfit originally designed for the Kingdom Hearts version of Rikku.
Squall from Final Fantasy VIII was originally designed with longer hair — and Leon's appearance here is a reference of that.
Dummied Out: According to unused files and code, It was originally planned for Sora to also be able to summon Bahamut, a ferocious, dragon deity that is a recurring character through out the Final Fantasy series.
Fandom Nod: Aurora's dress is colored purple on her illustration during the Awakening. This is a nod to the Sleeping Beauty fandom sometimes offering purple as a compromise to the pink and blue color war the fairies have.
Limited Special Collector's Ultimate Edition: Several months after the game was released in Japan, a Final Mix version was made with extra content and a new secret ending. This version later got included in the 1.5 ReMix.
Disney Castle was intended to be a playable world, but it was removed relatively late in development. Despite this, its icon still appears on the world select map, unable to be interacted with by the player.
Early trailers suggest that Donald and Goofy were supposed to wear their classic outfits from the cartoons before they were given new, more fantastical clothing designs. In the final scene of the game, for no reason given, the two appear in their classic outfits which they hadn't worn at any prior point in the game.
Kōichi Yamadera, Kujira and the late Taro Ishida, respectively, voice Sebastian, Ursula and King Triton instead of Tsunehiko Kamijo, Kumiko Mori and Akira Kume.
Yuki Tokiwa voices Pinocchio instead of Ari Hatsuzawa.
Hiroshi Hatanaka voices Oogie Boogie instead of Atomu Kobayashi.
Several Disney characters from older films had different voice actors, due to their original actors being deceased or unavailable at the time. This includes:
Tress MacNeille replaced Verna Felton as the Queen of Hearts.
Kevin Michael Richardson replaced Samuel E. Wright as the voice of Sebastian. This was the first time someone other than Wright voiced the character.
Due to the characters being much younger than their canon counterparts, Tidus and Wakka have different voice actors. Tidus is voiced by Sean Fleming instead of James Arnold Taylor,note and Cree Summer as a kid, making Fleming a double Other Darrin while Wakka is voiced by Dee Bradley Baker instead of John DiMaggio.
The German voice of Hercules is an interesting case. In the movie, he was voiced by Til Schweiger, while in Kingdom Hearts, he's voiced by Dominik Auer, who actually voiced young Hercules in both the movie and the TV show.
Interestingly, Seth Adkins reprises the role of Pinocchio — not from any previous appearance of the Disney Animated Canon version of the character, but from Geppetto.
Screwed by the Lawyers: The reason Mickey doesn't have a major role in the game is because he was being used for Capcom's Disney's Magical Mirror Starring Mickey Mouse, and they weren't willing to share the character rights with Square. After heavy negotiation, Capcom agreed to allow Mickey in one scene as long he was in silhouette.
Serendipity Writes the Plot: The Final Fantasy characters were included so as not to create new characters to fill minor roles.
Sleeper Hit: The game was this for Squaresoft following the very polarizing reception it received when it was first announced.
A popular story regarding the original concept for the game had Mickey as the main character, with Donald and Goofy helping out. The development team eventually became divided over whether Mickey or Donald should be the true main character. As a result, they compromised by creating Sora. This has never been confirmed nor denied.
It's rumored that Ariel was going to be a Princess of Heart originally, but they couldn't find a way to work her getting legs and captured by Maleficent after defeating Ursula — and thus was hastily replaced with Alice at the last minute.
Rumors existed that defeating Riku on Destiny Islands caused the initial fight with him in Hollow Bastion to become more difficult, but these rumors are false, as Riku's stats are the same regardless of whether you win or lose the fight on Destiny Islands.
The original scenario involved Sora saving the Princesses of Heart with the assistance of their respective princes, who join him in storming Hollow Bastion. In the end, only Beast joins Sora for his journey through the castle, Aladdin is told he cannot join him due to the world order, and the other respective princes don't appear at all.
Sora's original design was more lion-like and wielded a chainsaw sword. This was changed to a giant key to be less violent. In the games' Ultimania, Word of God states that the lion design for Sora was scrapped due to overlapping with the development of Final Fantasy IX, making him appear too similar to Zidane Tribal.
Many early screenshots for the game showed Donald and Goofy wearing their classic outfits from the original Disney shorts. This was changed to the current attire they wear in the game at the request of Disney, presumably to give them more adventurous appearances, and they can only be seen wearing their classic attire in the game's epilogue.
A sequence from Kingdom Hearts III, The Final World, was originally meant to be portrayed in this game, but it was changed to Sora turning into a Heartless.
Kairi's role in Hollow Bastion was going to be larger due to Sora going to the Final World. Additionally, it had been toyed around with to make her playable at some point within the game, but that never materialized until years later with Kingdom Hearts III: Re𝄌Mind.
Bahamut, a recurring Final Fantasy character usually included as a Summon, was originally going to be featured. While it is possible to hack the game to include Bahamut in the Summons menu, choosing him will crash the game.
There was planned to be one more battle against Ansem-possessed Riku at the End of the World. It was very nearly completed, but Dummied Out in the final version. It would have taken place on a crumbling island — which would have been a remnant of the Destiny Islands, consumed by darkness.
Before Ansem was created, Chernabog was going to be the final boss, being the embodiment of all darkness. This was changed for various reasons. Some concept art shows that the battle would take place at Hollow Bastion as he would have emerged from the Final Keyhole. End of the World was not created until after Ansem was.
On the same beat, the game's story was originally simpler and would've ended with the defeat of Maleficent. However, Nomura was warned that the game wouldn't sell well if the story wasn't more complex, thus came the creation of Ansem and a deeper story with more twists.
Some concept art showed Sora wearing a loincloth in the Deep Jungle and a world icon for a Toy Story world.
A world based on The Lion King was planned, but Square did not have the technology necessary to make Sora's lion model function properly. Instead, Simba only appears as a summon and the world was eventually featured in Kingdom Hearts II.
Disney Castle was going to be a playable world and was shown in the game's beta trailer. Although it was removed, it can be accessed with a cheat device since it still appears in cutscenes.
Aerith was originally going to have her name spelled the same way it was in the parent game. But as it was changed late in development, you never hear the other characters say it aloud. Her name is not actually spoken aloud in the Compilation until Crisis Core.
Aerith's role in the game was originally going to be filled by Aya from Parasite Eve until staff who'd worked on Final Fantasy VII requested it be Aerith instead.
Nomura planned for Irvine from Final Fantasy VIII to be part of Destiny Island's Final Fantasy trio. He couldn't come up with a design to fit the island theme, however, so he used Wakka — whose design is already fit for the beach setting — instead.
"Destati" is apparently considered cursed by the production team due to odd incidents — the worst being the entire building losing power — occurring whenever the vocal track was inserted into a piece of background music.
For the remastered version of the Final Mix re-releases, Nomura himself stated that the team had to rewrite the whole code of the game from what was available from the original since the source code was somehow lost, which led to a ton of research, and stated that "it wasn't easy trying to recreate everything in HD from there".
While some character models were massively updated for the HD remaster, other models, such as Sora and Ansem's, were instead ripped from Kingdom Hearts 3D [Dream Drop Distance].
This is the only game in the series to be released under the Squaresoft name, as their merger with Enix to become Square Enix happened a year after its initial release. The Square Enix logo would then appear on the packaging for the Greatest Hits re-release, though the Squaresoft logo still appeared as part of the logo and in the game itself; the logo would be updated in-game to have the Square Enix logo in the HD remaster of Final Mix.
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