I've just played it today (after buying it last night) and I like it even more than I thought I would. The learning curve is wonderful so far, not nearly as hard and unforgiving as Zen Puzzle Garden. Seeing the cute middle animals move around while they're waiting is really the icing on the cake - or should that be the castle?
But is it just me, or does the rabbit move around a lot more than the other animals? That's all right, as it's only natural that some people should be more fidgety than others, but I sometimes wish that the others would do something more interesting.
The only thing I really don't like about Chocolate Caste is that black bar between the playing field and the menu. I know someone else requested it, but I hate it. :P
Why not just use the same effect that you did on Neko Puzzle? It worked beautifully enough in that game. And I know it wouldn't make geographical sense to have the castle in the background when you're supposed to be inside it, but since when did Lexaloffle World abide by such restrictive laws of earthly science?
The animals all fidget at the same rate, but it's only when they're next to some chocolate that's the same colour as them. They take glances at it. If they're just sitting somewhere by themselves, they just blink. Perhaps it would be nicer if they did more though - like if they started chatting to each other if you put them closeby. I must think about that.
The black line stays! I tried a few things, but I couldn't get the colours to play nicely together when they were touching. I'll put in an undocumented black line removal feature in the next version though  (:
That's a good point about seeing the castle that you're inside. It's as if the castle thing is a front, and you actually get whisked away to a little sound stage somewhere without knowing it. There's always the Howl's moving castle explanation though.