There could have been an animated "Kingdom Hearts" series by Disney and Square Enix.
According to a video "Kingdom Hearts Part 2" uploaded by "DidYouKnowGaming?" two days ago, Disney and Square Enix had proceeded into an animated series adaptation of the video titled "Kingdom Hearts." They hired Disney's Animation Division Story Board Artist Seth Kearsley to write and direct the animated project. With complete creative freedom, he created his own interpretation of Sora's journey through world's from Disney's Aladdin lore.
Unfortunately, even if the story board, which was uploaded in part in the Internet in 2013 for testing, was well received by many fans, the animated series never saw the light of day. The reason was mainly because Kearsley's version was "vastly a different interpretation of the 'Kingdom Hearts' story." Besides the animated series that was never picked up, the video also pointed out computer generated trailers that were never seen in the "Kingdom Hearts" games and the differences between the Japanese version and North American versions of the game.
DidYouKnowGaming? is a site dedicated to making videos that discuss trivia's for various video games.
Meanwhile, according to IGN, the cancelled animated production was reported to have been done after the success of the first "Kingdom Hearts" that was released in 2002 exclusively for Sony's PlayStation 2. So the animated series for "Kingdom Hearts" was rarely talked about because it was never released in the first place.
Currently, Square Enix is still working on "Kingdom Hearts III" for release on both Xbox One and PlayStation 4. It was also reported that the date of released has been decided internally but still being withheld from the public. So far, the public only knows that the game will be released sometime in 2016 with rumors suggesting that it will include worlds from "Big Hero 6" and that it's game play will be featured in "Kingdom Hearts HD 2.8 Final Chapter Prologue."