One of my Sims has his face stuck in this dull, blank expression, literally frozen. Even while he's talking or hammering away at his anvil, he's pretty much "T_T" the whole time. I tried resetting the game and even going in the Edit In CAS. Anyone else have this problem?

I have a similar problem, except my sim's face is stuck with one eyebrow up, one down and her mouth in a 'grrr' pose. You can fix it by turing the ageSimsCheat on, aging them to another age then aging them back. This causes the programme to reload the sims body mesh. Hopefully this should help. x

If you have sims cheats on, try reseting the sim.
Worked for mine when it had a stuck arm.

kawaiipd beat me to ResetSim. If that doesn't work, Edit in CAS and make a minor change to the face (you may have to accept the change for anything to happen). If all else fails it is possible deleting your cache files could help, TSM stores some meshes and stuff in these for quick loading, but occaisionally they get messed up.