Behind Character Development

This is a question I've always wanted to ask other writers: "Do you have a real person in mind when you are creating and describing a character?"
I don't mean the character's personality or motivations, but their physical attributes. I think it might be mildly interesting to know who some of our favorite authors were thinking of when they were creating their characters.
In my case, the answer is yes. My characters' physical appearance is based on people I know or have seen on television or in movies. I'm a bit reluctant to identify any of those people now, because a) I often don't know their names, and b) if I did, I know the reaction would be, "But she's nothing like the person you described."
To which I would reply, "Yes, that's the point."
When I needed to describe BB Hughes' appearance, for example, I had in mind an actor I had seen on television (but whose name I don't know). The actor became, for lack of a better term, the "body model" for BB Hughes. It doesn't matter that their personalities are different, this actor had some of the physical attributes that I imagined for BB, so he became the visual model.