After spending the past week trying to figure out the layout of the castle in the Everfree Forest, I have concluded that whoever animated Mare in the Moon Part Two had no idea what they were doing. Time to invoke my oldest, most faithful friend: Creative license!
As long as you keep what they DO show relatively accurate I don't see anyone complaining with unique elaborations on what they don't show. Plenty of stories have done this with no problems.
But half of what they show makes no sense at all. I still can't figure out why there's a curving corridor leading into the Great Hall, when the Great Hall should be the first room in the keep. Or, for that matter, where the dickens the Great Hall is in the keep. It's got windows on either side, but the keep is small and rectangular, and while I might be able to accept that the Great Hall is the only room in the keep (though I'd seriously begin to question Celestia and Luna's architect), there's a curving corridor leading to it, which reduces the amount of space it could logically take up. Or why the gatehouse changes location between frames. In one shot, it's directly across from the pontoon bridge. In the next, it's gotten up and walked several meters to the left, rotated, and plopped itself back down. I eventually came to the conclusion that Lauren Faust was preemptively trolling me.