They have that joker smile that can look very unnatural a lot of times. The probably is that sims don't have much of personality in game and a lot of traits are simply just for show to make the player think they have personality. The forced smile is once again made to make the player believe their sims is feeling something when they aren't. In sims 3 and 2 we didn't need over the top smiles or auras to produce emotions out the sims, they were simply just there thanks to the point or trait system. Another thing I noticed is people complained about sims looking lifeless in the face in 3, they weren't lifeless they were realistic. People tend to forget that everyone has a resting face and that no one is smiling or frowning 24/7. This is why Ea felt the need to plaster that we happy few smiled on sim as way to get around actually giving sims in depth personality system that mix, match, and over lap each other and executed the right way.
