i think this has been suggested before.
so we've discussed "mounts" before, and there are currently farm animals like piggies and chickens.
we've also discussed "messenger" animals that could perhaps deliver small items over distances.
maybe piggies and chickens could be trained to be pets, but the way i'd like pets to work is a small cute thing that follows you around and provides:
a] a bonus to mood.
b] some special ability.
any ideas regarding pets?