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On the game's box-art, the clock on the tower to the left of the characters actually has thirteen roman numerals instead of twelve, and they are out of order. In addition to that, the two hands on the clock are pointing to 13 and the 7, representing the 7 lights and 13 darknesses that play a major role in this game's story. The clock tower itself bears a striking resemblance to the NTT Docomo building in Shinjuku, Japan.
Contributed by PirateGoofy
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In the Misty Stream area of the game, the player can find a wreckage of a pirate ship which appears to be the Phantom Storm boss from Kingdom Hearts 2, as can be seen by the identical jaw piece.
Contributed by Arcanus Zenbrk
According to Tetsuya Nomura, the aesthetic and environment design for part of the Hercules-based "Olympus" world was primarily inspired by California's Yosemite National Park, despite, story-wise, taking place in Ancient Greece. This decision came about when co-director Tai Yasue had visited the real-world location.
Contributed by PirateGoofy
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During a Square Enix Presents segment at E3 2015, Tetsuya Nomura revealed that the kingdom of Corona from Tangled was one of the first worlds to be considered for the game.
Contributed by CuriousUserX90
The Teacup Attraction Flow was originally going to be in a first-person perspective, however, this angle gave testers motion sickness and was changed to third-person instead.
Contributed by DrakeVagabond
Sora's costume is a combination of his costumes from Kingdom Hearts II and Kingdom Hearts 3D: Dream Drop Distance.
Contributed by DrakeVagabond
Kingdom Hearts III is the first Kingdom Hearts game to be on a Microsoft console.
Contributed by WhiteSamurott