This has been happening with my sims for awhile now. When I have a group of sims watch a movie together or TV channel as a group, only one or two will sit down while three of four stand even when there are empty couches and chairs sitting around.
Overall there's too much moving around when watching as a group. Even if my sims are standing and I force them to sit, other sims that were sitting will then stand up. It's annoying and looks weird.
Also, I wish they could make it so that you could get up during a movie and make popcorn without breaking the interaction. I always seem to forget to make the popcorn first and have to wait until the movie is over to start again because you can't cancel the other people from watching it.
