I got a rat. He was a nice rat.
He was a hungry rat and I tried to feed him bread/vegetables, but he did not want them. The only option I saw was to trade with him; I'm assuming that is the intended way.
Also, I couldn't figure out how to rename him either.
Lastly, I "dismissed" him so he wouldn't be starving but I couldn't bring him back. Does dismiss in this game mean 'let go'?