Odd Smiles

This is something I'm always paying attention to and trying to figure out. When people put out odd expressions, we can tell the real guy is smiling, but it's so close to the real frown, I want to be able to capture that subtlety in animation. (Course it's gonna take a great rig). This book helps me get closer. In this case I think maybe it's the inner eyebrows are not pulled down in the happy face, making the eye shape a little rounder, and there is a hint of the smile muscles in place bending the downward curve of the mouth into having some angles...maybe