A few things.
1. Non-ranty, curiosity. I'm writing an AU completely out of order where Kingdom Hearts is rewritten to include my Sue. After KHII it branches out into bigger AU territory, where the Organization comes back one member at a time, having to be fished back from Darkness one person at a time.
Here's where the curiosity comes in. Each member is fished back in the order of how close their power brings them to the Light. I was wondering what others thought that this order could be.
Ready. Set. GO!
2. Length apologies.
First off, last time I blabbed it was about Mary Sues and Self Inserts. My favorite genre. Also the worst.
I went on and on and on about the family and/or friends of MS's, and how little they are used. It also spawned a discussion about the usage of large families in fic.
Here I'm starting off with when you actually get to KH, instead of the prologue or plot device used to get there.
I apologize for length and overall bitchiness.
3. Beginnings are cool. Beginnings are also, in my opinion, the hardest damn thing to write. You want to get to the action, the drama, the romance! Newsflash, if your Sue is a Drop-In, they get to Riku SOMEHOW, and he most certainly will not fall in love with you at first sight! Nor would he do so in THIRTY SECONDS!
So your character comes from Earth. You have somehow plotted a way for your character to get to Traverse Town or Destiny Islands.
Two things now. Either your World is destroyed, or it isn't.
Most of the time people like to destroy their Worlds. It adds to the drama, allows your character to show off, fight, run, cry, whatever. Your family and friends are lost, though you will probably ignore one of those parties because it's not like you can focus on BOTH, now is it? How are they lost? Do you know what happened to them?
Your World is gone. Or you're gone from your World. Whatever. The point is that at this point your magical teleportation into the KH World has happened. Whee. You may or may not have a Keyblade at this point, or even a weapon at all.
Where are you?
People like to stick with three places. Traverse Town, Castle Oblivion, and Twilight Town. Four if you count the virtual Twilight Town. Then again, there are also a good number dropped in the World that Never Was.
If you go to Traverse Town, be aware that you could choose for your character to arrive at ANY TIME PRIOR TO IT'S DESTRUCTION. That means that you could have your character fall there shortly after the fall of Radiant Garden, while the pickings are good for settling down long term, and it would be easier to put your Sue in a position where they could become friends with Leon and the rest. It might not be a good idea to give your character a Keyblade though, unless they deliberately hide it, for the purpose of maintaining the plot.
So there is an eight to nine year period that you could drop-in on. 'Don't look at me, just another survivor-'
You could also age with the gang. You go there at fifteen or sixteen, you leave twenty-three or twenty-four. Then you could drag out a whole other story about going home, aged, legally an adult, married, and your parents haven't changed a bit. You're still in high school. You don't have your Driver's License. You jump at small noises, and have to restrain yourself before you Summon or pull out a weapon.
Then there's the period that where Sora shows up. His first visit. Do you arrive days before him, and decide that since you don't know the time period, you'll stay, and when he shows up watch him go? Do you show up minutes before he does, or after, and try to go with him? Or do you show up after he's left, having formed his party already?
The first of those would be a great one-shot. The second, however, is what usually happens. Now, most of the time I don't even see a reason for the Sue to accompany Sora. Why should he let them? It's not like they've met, and Sora is more concerned with things other than your Sue, like Riku and Kairi.
I suppose that Sora, being the goodhearted kid he is, wouldn't say no to a kid who's in the same boat he is. Lost, World gone, looking for friends... Fun. Also a plausible explanation for you going with Donald and Goofy as well. Sora might push for you to go so you can look for your friends too. Of course, Donald and Goofy won't risk pissing Sora off until they're sure he won't back out of helping find the King.
There is one more likely scenario that I see hinged on the plot device that everyone will groan at: The Keyblade.
A SPECIAL weapon. A weapon that can ONLY be used by Sora, Riku, Kairi, and Super-Mouse. And those who came before, of course. And Roxas, possibly Naminé. Ha. I have nothing against in including excess Keyblades, but often enough people will give half-assed explanations for them, or just copy the purpose of Sora's. No, you are NOT the one who will open the door. But it would be really really nice if someone could actually do this well enough that I don't want to imitate the mummification process with a fish hook and a spoon.
Now because I doubt that anyone will be willing to actually be ORIGINAL in the Sue/Stu Club, we'll go along with the going with Sora one.
You need a weapon. No way in hell are Donald and Goofy going to let you go without you being able to defend yourself, no matter how good of a buddy you are to Sora. Thus, Keyblade. Easy solution.
Let's go further. Maybe your character learned to use a sword back home. Maybe you're good at hand to hand. I imagine that you could get a suitable weapon in the Accessories Shop. Even if you can not possibly imagine that there are more buyable weapons in KH than Donald's staffs and Goofy's shields, I assure you that logic prevails, and you could buy such items from SOMEWHERE. Aladdin had a scimitar. Beast used claws. Ariel used fins/magic. Leon and Cloud and Sephiroth had pretty swords. Riku had a sword for a little while. Spears, guns, bows and arrows!
Even further now. Anyone remember the Traverse Town periods? When you first control Sora, it has to be anywhere from eight o'clock to nine at night. Sora hasn't had dinner, remember? He wakes up and explores, which judging from the town could take and hour or two, while killing Heartless. He heads back to First, hungry and with Munny. Heartless in first. Cid kicks him out to deal with them. Leon beats you up. Or you pass out. Then you have the option of heading from Second to First or Third Districts. If you go to First, you're told that first is safe and that Leon and them have cleared the place out. If you go to Third you get to fight the big bad for Traverse Town with Donald and Goofy. Fast forward. You now have the opportunity to leave the town and continue the game in Wonderland. Did they really?
By that time it had to have been one in the morning. Sora has been active all day and night, and hasn't eaten. There was a reason that you find Leon, Yuffie, and Aerith in the Café in First. They're eating! So you eat too. Then you take advantage of their hospitality and stay the night at the Hotel, where Goofy teaches you how to dodge while you wait for the Gummi Ship to be upgraded by the anonymous garage owner. Wait!
Now pretend your Sue is in the middle of this mess. At this point, neither she nor Sora have spare clothes or other important items. Since Donald and Goofy have done their shopping already, and have 'errands' to do, you go shopping on your own. When you meet up with Donald and Goofy later, you take note of a strange door in Third. Someone hits it with fire (on accident, of course) and it opens. Voila! Your character now has its weapon! She learns magic from Merlin!