In the Proof of Existence area of the Castle That Never Was, there are panels for each of the Organization members, represented by that member's weapon. However, Zexion's panel is so damaged, it's impossible to see his weapon. This is due to his weapon not being revealed in Kingdom Hearts: Chain of Memories, as the player never fought him.

Cloud's appearance in Kingdom Hearts II was based off of his appearance in Final Fantasy VII: Advent Children.

This was Pat Morita's final acting role before his death in 2005. He was reprising his role as The Emperor of China from Mulan.

Members of Organization XIII were supposed to be enemies in Olympus Coliseum battles, but were left out of the original game's release due to time constraints. They were later included in the Final Mix version of the game.

According to Tetsuya Nomura, the idea to put Sea-Salt Ice-Cream in the game came from the time he went to Tokyo DisneySea, where they sold this type of ice cream. He stated he liked the treat so much, he asked Disney if he could put it into the game as a treat the kids in Twilight Town ate during summer vacation.

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.

The Fenrir Keyblade's appearance in Kingdom Hearts II 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.

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. This is one example of many changes from the Japanese version.

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 first Disney villain 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.

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.

Selphie incorrectly refers to Tidus as "Tie-Dus" instead of the correct pronunciation of "Tee-dus" during a cutscene with Kairi.