The voice actress for young Kairi in both Japanese and English (Sumire Morohoshi and Ariel Winter, respectively) shares the voice for characters in other Square Enix works: Marlene Wallace and Mog, who are also cute, small characters.
Before names were released, Master Xehanort was referred to as OBM (Old Bald Man; in the vein of BHK/Blond-Haired Kid for Roxas). When his name was released, we got affectionate nicknames such as Baldinort, Baldsem, Geezernort, Oldynort, and Grampinort.
There's the Captain Obvious-styled Evil!Sora for Vanitas. The epilogue also gave birth to (as seen below) KH!Jesus for Sora.
As well as Jesusora.
A less common one for Vanitas: Soranitas.
Red Eye for the unnamed Heartless that serves as the boss of the Secret Episode.
Fan Translation: With the Final Mix version of this game. Like KHII FM, BBS FM was translated to English, this time thanks to Key To Truth. You must patch the game itself in order to play it in English, which you can do with either an ISO (for Emulation) or with an actual game cartridge.
That said, it's been confirmed by Nomura that he is making another Kingdom Hearts HD Collection for the PS3, and since the ending credits to 1.5 had images of KHII FM, BBS FM, and Re:Coded, its being assumed that the next collection will contain those games, and will be brought to the U.S., meaning that BBS FM will get an official translation, making the previous one null and void.
Freeze-Frame Bonus: More of a blooper, though, but before fighting the Unversed alongside Mickey in Radiant Garden, if you look carefully behind Aqua, you can see a second Kairi right behind her.
Sora's gonna save Terra, Aqua, and Ven from their fates.
On February 2009, a troper speculated the possible connection between the armor Xemnas wears in Kingdom Hearts II and the armor the protagonists wear. Two years later we got Birth by Sleep: Final Mix, aaaaand...
Bret Iwan replacing the late Wayne Allwine as Mickey. Surprisingly averted by Chris Sanders, who still reprised his role as Stitch despite now working forDreamWorks Animation, Disney's primary rival in animated films, following behind-the-scenes conflicts on Bolt.
In the Japanese version, Captain Hook is voiced by Naoya Uchida instead of Chikao Otsuka, presumably because the latter voice actor was also voicing Master Xehanort.
Talking to Himself: Averted in the case of Captain Hook due to The Other Darrin (Naoya Uchida, who in fact is the usual Other Darrin for the Japanese Hook); in the rest of the series and in the Japanese dub of Peter Pan, Hook is voiced by Chikao Ohtsuka. Ohtsuka's in this game, but is playing Master Xehanort. And even if Ohtsuka did voice Hook here, the pirate and Master Xehanort do not cross paths anyways.
Played straight in the English dub by David Ogden Stiers, who plays two of the seven dwarfs (Doc and Happy); Russi Taylor, who plays Minnie, Huey, Dewie, and Louie, as well as the Fairy Godmother and Drizella (though the two don't have any scenes together); and Jim Cummings, who plays Pooh and Tigger. And that's just naming the characters who share worlds together! The actors mentioned (and a few not mentioned) play other characters as well, though those characters aren't even in the same world as each other.
Nomura considered showing Leon and Cloud's past in the game, but decided against it because the Radiant Garden would have been overloaded with characters. And because, in his words, this game is complicated enough as it is.
Also, a Jungle Book world was going to be featured, but was pulled out. As one of the cut rooms was Louie's throne room, it may have been axed because of Disney's Louie embargo (see the Screwed by the Lawyers page's entry on TaleSpin).
Pleakley would've made an appearance in Deep Space.
The "Birth by Sleep: Volume Two" secret ending of Final Mix hints at a sequel for the PS Vita...that Nomura has now confirmed will not happen, as executive producers, for better or worse, thought there had been more than enough portable KH games, so the project was scrapped and focus was put solely on developing Dream Drop Distance and Kingdom Hearts III.