See How Shadows Are Changing This Character's Face
Shadows Make This Character's Face Change In The Creepiest Way
Try making your own version.
3D Artist known on Reddit as QuestionableHoney recently showcased a PS2-style model that has different faces depending on whether they are in shadow or not. It's a neat concept with a neat execution, and the artist's next goal is to figure out how to make the colors look nice and vibrant while still preserving the shadow effect.
If you want to try it and create your own version, you can use the approach suggested by Noblebatterfly. This technique doesn't work in Cycles, though.
"Basically, you make two versions of the texture and have two shader setups that you combine with a mix shader node. For the factor, you make a mask purely out of your light with the help of a Shader to RGB node.
Instead of the two upper diffuse BSDFs, you can use any kind of shader setups, it doesn't really matter, but it will work best with a cartoony cell shading."
