Axel was originally meant to die at the end of the prologue. However, due to him being a fan and staff favorite, his role in the series was expanded upon.
There is an alternate version of Twilight Town's theme titled "Lazy Afternoons" that is unused in the game but appears on the official sound track.
Many Scenes in the world Port Royal are changed in the Western release. William does not put a gun to his head, Barbosa's Sword is never seen through Jacks chest, and blood is not present on the medallion after the cut scene.
Through the use of a cheating device, 2 alternate versions of the Ultima Weapon can be found. These weapons are titled "Edge of Ultima" and "Detection Saber". In game they are given a glitched appearance and are only palette swaps of the original Ultima Weapon. They are also missing a menu picture, and instead a map is displayed.
According to the trailer, the castle at Hollow Bastion from the first game may have been where Sora first met Organization XIII, instead of in the bailey like in the final version.
Contributed by Soundcardboard
The Fenrir Keyblade's appearance in Kingdom Hearts 2 is based on a pin tumbler lock key unlike all other Keyblades. The name comes from Norse mythology and is also a reference to Cloud's motorcycle in Final Fantasy VII Advent Children.
Chicken Little was included in the game as a summon to promote the movie, which had not been released in Japan at the time. He is also the first CG movie character to appear in the series.
Contributed by Pogue-Mahone
Xigbar's weapon was changed for the American release. In the Japanese version, he carried a weapon that resembled a sniper rifle and his scope included a cross-hair while zoomed in. In the American release, his weapon was changed to look less like an actual rifle. His weapon was split into two blades, and his scope was changed to include a three circles design instead of a cross-hair.
In a beta picture of "The Battle of the 1000" at Hollow Bastion, there appears to be two Behemoths standing in the middle of the heartless army with Sora, Donald and Goofy charging at them. This would imply that you would fight more types of heartless than the Armored Knights and Surveillance Robots. Also that Donald and Goofy would be a part of the battle. According an interview with the director, Tetsuya Nomura, the battle was so big that the team almost dropped it from the game even without the extra heartless, due to the sheer quantity of enemies on screen.
Gaston's absence from the "Beauty and the Beast" world (Beast's Castle) makes him the only Disney villain so far to not appear in the Kingdom Hearts series with a world based on his movie featured as a playable level.
Originally, the final boss, Xemnas, was going to have another final form.
Contributed by DidYouKnowGaming
Toy Story's Woody and Buzz were set to appear as summons in Final Mix, but were removed for unknown reasons. These models were found in the code, untextured, and amongst the game's summons.
Contributed by Dazz
Selphie incorrectly refers to Tidus as "Tie-Dus" instead of the correct pronunciation of "Tee-dus" during a cutscene with Kairi.