I use to have three pet rats. Two white rats that were meant to be feeder rats. They were extremely smart, but since they were born and lived in a fish tank, they could barely run or jump. So I got to watch them as they learned to be rats. I taught them to come when I called their names, and I would let them run loose in my apartment when I left for work, after a lot of training. They would come running out to greet me when I would come home. One of them would tuck me in and give me a little rat kiss before I would put them in their cage for the night.
Sadly one had a very serious thyroid condition, which made her obese, plus she had a very large tumor. She seemed to have died in her sleep peacefully in September of 09. Then, much to my shock and horror, her sister choked on a piece of popcorn. I was heart broken.
The third one I got on a spur of a moment decision, the poor dear was all alone in her little cage at the pet shop and I took pity and bought her. I never managed to get the thing trained, and would bite my fingers to the point where they would bleed. My other rats would give me nips, but never drew blood, even when they were really pissed off with me.
Oh how I miss my two white rats, they will always have a place in my heart.