Not sure exactly what the rectangular growth on the rabbit's back is, but c'mon, that's a pretty good rabbit for a 3 1/2 year old, eh? Seriously, this kid is pretty good. His fine motor skills are really taking off. He gets so detailed in his coloring lately, and can write letters almost as well as Caleb. It's fun to see his artistic bent, but it is going to be a challenge to his un-artistic parents to nurture it!