Ah, how absolutely adorable! The amount of exquisite detail you poured into this piece is really incredible; I love being able to notice all sorts of small things like the bats in the distance, and the jack-o-lanterns packed full of candy. The characters themselves are very well drawn and animated, and you arranged the composition in such a way that the entire piece is pleasing to the eye as a whole! The soft round cloud-like edges and jaggedy rocks add so much more dimension to this piece! My main suggestion for improvement would perhaps be to take the light sources into consideration for the characters and the floating rock. Since there is a lantern and a moon to the character's backs, this work could benefit a lot by adding in some subtle indication of backlight. That's really just a nitpicky thing though; gorgeous GORGEOUS work!
COOL! I love how the lantern looks like a face, and the chibis: "What, nothing strange here." Small nitpick - it's a little hard to see their noses and mouths, though that could just be my computer. I like it!