While pretty much every entry in the Kingdom Hearts franchise has a secret ending, the original title in the series is on the list simply because it did it first. Astute players were rewarded for collecting everything in the game and completing every quest, including the bad-ass Sephiroth Colosseum battle. Other tasks included: completing the Hades cup, finding all 99 Dalmatians, and sealing every keyhole in the game. Or beating the game on the expert difficulty. After investing 60-80 hours players were met with the relief that their grand adventure in the Kingdom Hearts universe was far from over with this secret ending.
Questions abounded. Who the hell is this robed dude? Is that Riku on top of that skyscraper? Why are the heartless so buff? And OMGWTF two keyblades?!
While the Kingdom Hearts secret ending certainly provided info about the upcoming sequel, game director Tetsuya Nomura included the ending as a concept of what he wanted out of a sequel, much darker tone and more action. Nothing in the ending was ever meant to be included in the actual story for Kingdom Hearts 2. And, as all devout Kingdom Hearts fans would have to get used to, the answers to all their questions would not come for quite some time.