I have 4 female mice who live together in an Imac. They are very inquisitive. The cats sit in front of the cage and the mice sniff and look at them a bit. Their facial expression does change a little bit...their eyes widen and brighten up when you give them something new to play with...just like children really.
They also run around a lot faster when you have cleaned their cage out. They have to examine every inch of the place, even if the same objects were in the same place before. They do not all follow each other around though. They don't mind sleeping on their own or eating on their own.
Unlike hamsters, they are not tidy rodents. Hamsters will move their food to where they want it...ie their bed...but mice will just make mess everywhere. They tend not to take food anywhere else at all.
With regards their body posture, they are either on 2 feet or 4.
I have never seen them put their ears down, always sticking up. They sit on their bums to clean... (not really sure what you are looking for here) and they love to climb.
Now, the cutest thing about mice is their noises. They squeak alot!!! Not loudly or nastily, just cute little squeaking. When playing, when eating, when in their houses. I think it is some sort of communication. But I can't understand! lol.
Anything else, just PM me!!