Yep. The fantasy serial I'm writing (and putting out chapters of 2-4 times a month) grew from an idea I had for a D&D character whose purely for flavour background was that he had been "polymorphed" from a baby bird into a baby human and then raised human. I thought the various polymorph spells in D&D loaned themselves to all kinds of fascinating story ideas. This eventually grew into my fantasy world idea where an Empire is based on the bedrock of a slave class that was entirely made up of animals transformed into humans and raised to be slaves from day one. A version of that original character will make his way into the stories I'm writing. Like many others have said too I think that a lot of the characters (or at least pieces of them) I've created over the years will show their heads now and then in what I write.
Now that sounds very interesting. Would these people have animal or human natures?