Early concept art shows that Sora would have originally donned Aladdin-inspired shoes and a more street rat-inspired version of his usual wear when he was in Agrabah, but in the released version he just wears his normal outfit instead.

Early screenshots of the game showed Sora with different clothes that were orange and black and a different hairstyle that was black but with large white tufts sticking out the front of it. This early design for the character also resembles the earlier "Lion Sora" design, albeit without the lion elements.

A Station of Awakening for Alice from Wonderland was originally created and planned to appear in this game and accompany the Belle, Cinderella, Aurora, and Snow-White ones but ended up never being used. Spoiler:With a possible explanation being the fact that Alice, like Kairi and Jasmine and unlike the other Princesses of Heart, was not abducted by the Disney villains at the very start of the game.

If you defeat Maleficent in Hollow Bastion before chasing Pinocchio in Monstro, a set of alternate cutscenes will play out as you progress through the rest of Monstro. The cutscenes where Riku talks to Sora in the first chamber of Monstro, and the cutscene where he talks to Maleficent are both edited out of this sequence.

In each Dive to the Heart segment in almost every game in the series, there is a disembodied voice that can only speak through text that guides the characters (and thus the player as well) through the tutorial of each game. The identity of these voices has been unidentified in every game but Kingdom Hearts: Birth by Sleep (where it is obviously child Sora) and the first Kingdom Hearts. For the latter, in the Kingdom Hearts Ultimania, Nomura was asked who the voice is for the opening of the first game and he finally gave it's identity as being none other than King Mickey. However, this interview was done in the early 2000's before most of the sequels were produced, so it's unknown if this explanation was retconned or not.

In the Bizarre Room in Wonderland, the fireplace's flames can be "put out" if Sora attacks the fireplace's grated opening with a Blizzard spell, and it can be lit anew if the grated opening is hit with Fire magic instead. Being able to put out the fire makes the second phase of the Trickmaster Heartless boss fight even easier, as the frantic boss cannot light their juggling apparatuses and fling their own Fire at Sora. This is also possibly why the Cheshire Cat gifts Sora a Blizzard spell/upgrade when Sora obtains and shows him at least the Claw Marks piece of evidence during Alice's trail, and also why the grated opening itself is able to be locked onto.

Completing the world "Deep Jungle" before Wonderland will cause Snow White to be kidnapped instead of Alice in the cut scene which is shown after completing Deep Jungle.

In the Secret Place, on Destiny Islands, the walls are covered in paintings which seem to foreshadow some of the earlier events in the game. For instance, there is a painting of Sora winning at the coliseum; the tree house from Deep Jungle; and Pluto waking Sora up in Traverse Town.

Sora was not originally the main protagonist of the series. In the beginning, Disney had desired Donald Duck to be the protagonist, while Squaresoft wanted Mickey Mouse. Series creator Tetsuya Nomura wanted neither and developed an original character based off of Disney's style. In the end, Sora was created. His yellow shoes, red shorts and white gloves are based on Mickey Mouse.

According to some concept art released by Square Enix, Sora was originally not going to wield a Keyblade at all, but a chainsaw sword instead. He was also going to have a design with lions fur, claws, a tail and ears.

Bahamut, a recurring summoned creature from the Final Fantasy series, was planned to be a summon for Sora. But it was removed from the final version. Searching through the game data, a Bahamut summon option can be chosen through the use of cheat codes. However, since there is nothing to execute when it is chosen, the game will crash.

The secret ending, "Another side, Another story," was not meant to be a real game. It was only there to show off ideas that Tetsuya Nomura had for the sequels. It was not until Kingdom Hearts 358/2 Days that the fight shown was playable.

Disney Castle was supposed to be playable. It was shown in a beta trailer but the level was cut from the final version. However, through cheat codes, it can be accessed.

In the Japanese version of Kingdom Hearts, the Chernabog fight does not have the "Night on Bald Mountain" music. Instead the regular boss music will play. The "Night on Bald Mountain" music was added to the international release to make the scene more true to the scene from Fantasia. The music was added into the Final Mix version of the game.

If you enter the Hercules Cup time trial, get to Hercules, pause the game and choose to restart the time trial, it will take you back to the start of the Hercules fight and the timer will be frozen at 00'06"23.

There was a planned boss battle with Riku who would be possessed by Ansem in an area titled Crumbling Island at the End of The World which was based off of Destiny Island, but devoured by the darkness.

In Deep Jungle, outside of the tents on a table is a pot and cup which bare a resemblance to Ms. Potts and Chip from Beauty and the Beast. These characters also appeared in the Tarzan film.

A red Trinity can be found in Halloween Town that must be collected before Spoiler:Oogie Boogie is defeated, otherwise it will become impossible to collect and the player will be unable to get a 100% completion rating in Jiminy's Journal. The red trinity is located Spoiler:inside Oogie's Manor, which disappears when Oogie is defeated. This was later fixed on the Final Mix release of the game by relocating the Trinity to the ground.

The enemy "Assault Rider" was meant to appear in the game but its style didn't fit any of the worlds so it was removed and used in Kingdom Hearts 2 instead.

The ending to the beta trailer for the game shown at E3 2001 featured an alternate logo. The word "Kingdom" is shown in normal golden text while the word "Hearts" is displayed in a modified version of the final logo's spiky text. The trademark heart is also missing from this version of the logo.