Kids crafts - Halloween skeleton

Below was the homework my son done in last Halloween.

It was the story book cover.

He drew this by himself! I asked him why he knew how to draw the skeleton?

He said he saw this in a book that he read.

I think it is truly great! I like the sharp colors that he used around the skeleton.

But when you see carefully, there is a problem with its teeth!

How come it has three rows of teeth?? lol!

My son also laughed when I pointed out this careless mistake, lol!

How do you think about this skeleton??