Back legs. The front ones are OK, but the back ones are in a pretty... weird position. One of them lies on the other, which is not right for the position of the whole body. Even normal animals don't have their back legs in that position when they' lying on the ground like that.
The purpose for that pose was mainly because a mature version was wanted as well. And it is possible to twist your body in such a fashion. I admittedly may have not illustrated it that well, but it is definitely possible. It may not be an ideal resting position, but like I said, it was chosen for the purpose of showing off.