Necks don't turn that way without help. The chin should still be in front of the shoulder, and the shoulder should be twisting back and down a bit if you want to show they are turning their body to look back.

It's really nice work though. I like the butt part.

Bordering on Rob Liefeld territory

The proportions are a little off, but the coloring and texturing are top notch

ASSSSSSSSSS!