Expressions seem easy up fount but there is a lot of little subtle things that you don't realize until you go to try and recreate them.
Happy=Mouth turned up and sad=mount turned down; isn't always right. Sad faces can have raised cheeks like that of a smile,
but have eyes that are contorted like disgust; congratulations, you made sorrow.
Cartoon faces are almost ironically harder then realistic ones. Cartoon faces should be easy because they have so much more
flexibility then a real face. The problem is know how to use the flexibility and sometimes remembering that you are, in fact, working
with a face that NEEDS to be exaggerated to get the most effect.
It's tough stuff.