R. Daneel Olivaw. The R stands for robot, but he is made to look and act human, and has been endowed with the best qualities of a human. He gets his start as partner to detective Elijah Bailey. He had a tendency to pop up in books unexpectedly. He is probably my favorite Asimov character. I hope I am remembering and spelling these things correctly. It has been a few years since I read these books.