a friend of mine found a baby squirrel several months ago. it was so tiny it could be held cupped in her hand. she only kept it for a short while, just long enough so it could be fed and cared for until it was strong enough to live in the world on its own. it was kept in the house in a small cage for that period of time.
i suppose it can be considered a pet as when she let it go it really did not go far. it lives in her yard and will often scurry onto the carport when she is outside taking care of the plants out there. just a quick dash on and around, and, then off again, almost as if it is saying 'hey'.