Listening to the old soundtrack reminds me of some of my old headcanons, and this thread seems like a good place to dump the spergery:
1. Since Roxas is Sora's body, and he didn't rejoin him till the end of 2's prolonged, that means for the end of 1 and the entirety of Chain Sora is effectively a human shaped heartless like Ansem SoD. And for most of 2 he's a heartless possessing a nobody. This explains his increased cold-bloodedness in Chain and 2, as well as anti-form (Roxas is rejecting him, and Final form being the symbol of his acceptance means it reduces the chance of rejection.)
2. Axel and Roxas fucking hate seasalt ice cream. This is pretty much confirmed for Axel with the opening to days showing him almost puke when he first tastes it. Roxas you have to read his journal entries where whenever he eats it alone he can't say a single good thing about it. They only eat it because it reminds them of chilling with the homies after work. Xion, being a copy of Kairi who grew up under Ansem the wise, is the only one who actually has a taste for the stuff.
3. My favorite: Axel never got a keyblade. He just form changed his chakrams and has been faking it ever since. Whenever he has to exert himself he instinctively switches back. The only ones who notice are the keyblade masters. Yensid doesn't care because the light needs soldiers. Mickey and Riku notice too, but they know keyblades can be forged over time ala Way to Dawn so are cool with it. Xemnas notices and thinks it's ridiculous. Aqua notices and is livid at this actual fraud.
Anyone got any other theories?