When did you realize there were skeletons inside all of those cute anime girls?
Did you think this through OP?
Technically anon, the anime girls are inside the skeleton, not the other way around. I know! I couldn't believe it too the first time i heard it, but it's true!
2D girls inherently do not have an "inside". They don't have skeletons at all. They are only what you see on the surface. So what you assume would have been a simple and humerous observation actually turns out to be wrong.