I'll just repost what I said in the random thoughts thread:
"My sister and myself were walking this evening and had a whole out discussion about Andalite anatomy. Like how would organs be arranged and how things would work. No idea how that got started, but it lasted a good 15-20 minutes.
We talked about the placement of the hearts, how big their lungs would be. Where would organs be in the first place and would they have doubles of anything since they have the humanoid torso and the deer/horse back? What sort of digestive/elimination system would they have since they don't chew stuff? How big would an andalite baby be? How would their spine work since it has to curve from torso to deer/horse body and the tail.
Do they have double rib cages? I guess they'd have to in order to support everything."