He knows what you did for him. He will be eternally gratefull and stick to you like velcro. Sometimes there are very special cats with whom you form an inexplicable bond. This happened to me with a cat I looked after for a friend for two months one summer. I had to give Kashmir (she was a siamese a.k.a. velcro kitty) back. We were both traumatized by the seperation and it took months for us to get over this. I would visit my friend who lived in another city mainly to spend time with her cat. You two have many happy years. Hope he gets along well with the other cats and they are accepting of him. Are they showing any interest as to who is behind the door ?