Every time you enter a new floor, the previous floors rooms are reset. As Sora and the gang advance through Castle Oblivion, they begin forgetting important things. Meaning, they forgot how they set up the rooms and need to set them up again.
Once you know the basics of the plot, if you start Sora's storyline over, it becomes hard not to notice that pretty much every world's modified subplot deals with the manipulation and falsification of memories. Considering the circumstances, it is entirely possible that Namine is trying to send coded warnings to Sora that he's being brainwashed.
Marluxia's Viewer Gender Confusion makes a whole lot of sense when you consider that Marluxia was originally conceived as female.
During Kingdom Hearts: Chain of Memories in Reverse/Rebirth when Riku was being Mind Raped by Zexion and was thrown into an illusion that made him think he drowning in light, which is implied to have the ability to actually kill him off if Riku gave into it. Now Riku's in a position that if no one snaps him out of it, he will die. Of course Namine saves him and all, but where was the one who told him "You're not alone" in Riku's hour of greatest need? It might not be horrific to some, but the idea that everybody's childhood companion Mickey Mouse left someone to die is rather unnerving.
Add to that the fact Mickey later said that he originally believed that all darkness was bad no matter what, that includes those who wield darkness. Though the asshole other king (banished or not) in the room was kinda distracting.
But since it was only an illusion, it might not have physically harmed him, or perhaps Mickey couldn't tell he was in true danger.
Xion is a source of Fridge Horror but here's one thing that makes an already Nightmare Fuel loaded scenario even worse. When she was losing her ability to wield the Keyblade, Saix threatened to turn her into a Dusk a non-sentient Nobody. Terrifying concept on its own, except later we find out that she's not a Nobody but a Replica and one who would most likely have a strong enough will to become a humanoid Nobody. So Saix would've essentially been taking both the heart and soul of a teenage umm.... person.
Fridge Brilliance: Saix never threatened to turn Xion into a Dusk. Xion ASSUMED Saix would turn her into a Dusk, given that she'd seen him threaten other Nobodies with a similar fate. At this point, Xion didn't know she was a Replica, and so she was still under the impression that she was a Nobody like everybody else in the Organization. The flipside though is that what Saix would really have done if he had determined that Xion was completely useless would be to force Roxas to kill her.
Here's another little bit of Fridge Horror: how are the other Nobodies so certain Xemnas can turn them into Dusks?
Simple: In Dream Drop Distance it is revealed that Nobodies regrow their Hearts and since Dusks are Nobodies created from those with weaker Hearts than the stronger Nobodies Xemnas is likely capable of having the Organization members' Hearts removed causing their bodies to degenerate into lesser Nobodies(in other words Nobodies of Nobodies).
Consider the sheer number of worlds that were consumed by Heartless in the first game, and that many of them were canonically Disney movie worlds. Now remember that a Nobody is created when someone's Heart is consumed by the Heartless. In other words, there could be Nobodies out there that look and act just like your favorite Disney characters, and the only way to return them to normal would be to kill them.
A Nobody is only formed if the person who became a Heartless has an exceptionally strong heart. Usually the bodies just fade away.
Except none of the Nobodies act very convincingly like their somebodies, the lack of [[YMMV emotion]]
Oh don't worry, official word is that he was reconstituted as a full and whole person again. By which, we mean that Xehanort is back, whole and perfect again, and still in command of Terra's body.
Speaking of BBS, wasn't everyone so happy that the original beings of the Organization were all over the Radiant Garden? Tiny, derpy little Isa and Lea sure were adorable, huh? And bitty Ienzo... dawww. Except for the part where these kids get their hearts ripped out by hungry eldritch abominations and grow up to be everyone's favorite sociopaths Axel, Saix and Zexion. Think your adolescence was bad? Try going through puberty with extra existential angst!
The apprentices are implied to have volunatrily given up their hearts in the pods seen in Hollow Bastion/End of the World. Not hard to believe for some of them (read some of Xaldin's secret reports). That being said, yeah Lea and Isa probably 'get their hearts ripped out by hungry eldritch abominations'. Though neither Axel nor Saix are sociopaths, in terms of what that word actually means.
While we don't see what happened to Dilan and Aeleus (who may have gone willingly) we know at least Braig, Ienzo, and Even weren't willing.
Ventus is perhaps one of the nicest people you'll ever know...but he has an evil side...Vanitas. Vanitas would look like anyone who connected to him, hence why he looks like Sora. This not only means that if it's done to you and someone connects with your heart, you'll have someone with black hair looking exactly like someone who connected with your heart and healed you...and if just Vanitas was a monster from Ven, imagine what he would be like it it was someone who wasn't as nice as ven.
In the original Kingdom Hearts, before the battle against Ansem-possessed Riku there was that chamber with those giant crystals that had each Disney princess trapped in slumber. When you consider that these cherished princesses have all been kidnapped so that the Heartless could extract their hearts in order to open a hellish door of darkness, seeing those princesses hooked up like some sort of battery is fairly terrifying. Imagine if you were a fan of any given Disney princess, and you saw your favorite character in a crystal GETTING THEIR LIFE FORCE SUCKED OUT.
Ever taken a good, close look at the drawings in the Secret Place on Destiny Islands? Some of them are really, really unsettling.
And remember, those were drawn by Sora, Riku, and possibly Kairi.
From the ending of Kingdom Hearts II comes a particularly nasty piece of Fridge Horror. When Nobodies are "killed", they go to Kingdom Hearts to be reunited with their heartless half so they can become a whole person again. But Roxas' other half, Sora, was already in humanoid form, so Roxas got absorbed into his subconscious. In the ending, you can see that Roxas is still aware of what's going on around him. Now, honestly sit and think about the kind of position he's in. He's a fully self-aware consciousness that's trapped inside somebody else's head, who can't move, speak, or do anything else, only being able to watch somebody else live for the rest of his life. He's in an And I Must Scream situation and he can't even do that.
Where was it stated that Nobodies are reunited with their hearts when they're defeated? As I understand, you kill them, and they are gone. Frittering away out of existence, leaving nothing behind to remind the world they were even there, not even a body. Also, if you take the symbolism of the Two Become One keyblade and the Final Form. Roxas wasn't overwritten by Sora, they truly reunited, bringing together the two halves to complete the whole. By this, there's no Fridge Horror in that, just the realization that Roxas is the lucky one in the Organization... the only one who achieved the goal they all set out to achieve. He got his heart. Where the fridge horror comes in is that Nobodies have no hearts, and thus, no feelings, correct? Virtually everything can be claimed to be them "acting" but when they die, they show fear. True fear. Not so heartless now, are they?
It states it in RE:Coded's secret ending that a Nobody goes back to their hearts, as long as their hearts, now made into Heartless, get released first. Also, in KH2's ending, it showed Roxas in Sora, perfectly aware. We could infer that this means Roxas IS in fact self-aware even after merging with Sora.
Also Roxas with the Heart and body of Ventus, and flashes of Sora's memory wasn't really a part of Sora, he was a seperate entity with no memories of, for lack of a better term, Somebodyhood.
Briefly in Kingdom Hearts, Sora is turned into a Heartless, and later reverts into a human WITHOUT RETURNING TO HIS BODY. This means that Sora would've been a Heart and Consciousness in a body of darkness for the rest of the game and Chain of Memories.
That's exactly the point why Roxas must return to him in the KH II Prologue.
Think about it like this: Sora had to open his heart to free the princesses hearts, that turned him into a heartless, sure, he turned back into a human thanks to Kairi, but in the second game, he can turn into Anti-Sora, a heartless version of himself, which heavily implies if not outright states that Sora is still at least PARTIALLY heartless, and Nobodies are the mind and the soul of those people who lose their heart, so, if Sora is at least partially Heartless, and Roxas has got Sora's mind AND soul... How in the hell is Sora still alive?!
In a way he is like Xehanort's heartless. Xehanort's heartless had a body but no heart just like Sora. But Sora is very different being in that he NEVER got his heart back but fused with his nobody. After he became a heartless it was only Kairi's light that transformed him back to "normal". Being part-heartless, it is eventually brought up in the second game that he CAN transform into a heartless state (Anti-Sora). What will happen if this happens later on in the story?
All indications seem to be that ever since the Battle in the Center of the Mind, Roxas' will has been in tune with Sora's. We see him smile at the Alter of Naught and back on Destiny Islands. Once he got the angst of his system, he was actually happy to be reunited with his other half. Namine, whose experience was similar, had no qualms whatsoever about reuniting with Kairi, when she knew what the ramifications of that decision were.
At the beginning of Birth by Sleep, Ven is shown unconscious and wrapped in a white sheet (that makes him look either like an infant or a corpse, depending on how you look at it), which then disappears in his Dive to the Heart to show he's wearing nothing above his waist. On it's own, it's not that odd — just some death/rebirth symbolism, and maybe a bit of fanservice. But, later in the game, he's shown to have been fully clothed when Master Xehanort tore Vanitas out of his heart and left him comatose. The only way for him not to be wearing a shirt is if Master Xehanortpartially stripped an unconscious, eleven-year-old boy.
Dream Drop Distance adds whole new levels of Fridge Horror to the series, primarly thanks to Xehanort. Among these revelations: Braig isn't going grey due to age, he's slowly turning into another Xehanort and has been for the last decade. This is also happening to Isa, as evidenced by his change in eye color. In fact, this was the entire reason he put together Organization XIII. He needs a dozen extra hosts to divide his heart into, and each member was a potential vessel for him. Including Sora, since Riku didn't work out. He also intentionally lied to them about their true nature as Nobodies, and intended to use the Kingdom Hearts he had them forming to "regain our hearts" to STRIP THEM of the hearts they were ALREADY regaining, so they'd be proper empty shells for him to possess. Yikes.
Do you remember that part in Agrabah where Aladdin tricks Jafar into using his second wish? Yeah, no. Jafar never actually said "I wish..." so if anything, HE tricked Genie into doing crap for him for free.
However, Genie considered saving Aladdin's life in the movie as using up a wish, so maybe those rules also hold in this game.