they sqeak and the other usually sqeaks back
What the eat , drink , how they stay healthy and I guess what to shelter them in.
if you look at the top of their head, where the "crown" is, there will usually be little bugs crawling around , if you see them then your little pally has lice and you should take him/her to a vet...
It gets really fat. Fatter than it usually is. That's about it.
It may stay in its Igloo/House a lot. Or it may make some noises.