Fun fact: A pretty big part of The Sims 2’s marketing was about how Sims were reactionary and were more capable of reacting in context to certain things. In fact, a photo was released in development with all stand-alone emotions Sims are capable of showing.
While the sims are capable of making other faces to indicate emotion, those facial animations are dependant of an a full body animation they are performing. This list shows all of the facial animations independant of the rest of their body.
This is why Sim’s faces in TS2 get stuck sometimes. One of these animations got “stuck” to the sims face.
The Sims of San Myshuno 