I am very interested in speaking with the people you find in your dreams (only when lucid, that is)
Anyway I rarely find myself lucid enough to sit down with a person in my dream prepared to ask any question I wish. I fact I've only done it twice. The first time I asked an old man what he was. I wanted to know if he was a creation of my mind or something else. He was very elusive with his response, he pinched his elbow with his fingers and explained that his existence was like that of the pinched elbow. I understood that when you pinch your elbow very hard you tend not to feel pain.
The second time I spoke freely with a dream person was last night. I met a rather friendly character, and I was lucid for a while then finally mustered the confidence to ask him what he was. He was again very elusive. I asked him if he was human and he said no, then I asked if he was an animal and he said no. He then said to me that he was, in fact, a tree. In retrospect, I was rather dissapointed by his answer. It seemed to suggest that he was just a creation of my mind. But could it be possible that he was suggesting that he was sort sort of essence or spirit of a tree? After all, plants are "living" along with humans and animals. I then asked him what he thinks about, and he replied something like, "I think about everyone dying and leaving the earth." I then asked if he knew what happened when you die and left the earth, and he said no and that the idea scared him. I agreed.

Now, I would like to think that the people that I get a chance to ask questions to in my dreams are somehow seperate beings from myself. A lot of times if I look a dream person in the eyes and become confrontational, I suddenly feel extremely uncomfortable so I try very hard to be friendly. So far I have not had any solid evidence to suggest that these people aren't just creations of my imagination.

I have though, twice, encountered beings which I felt were much more powerful that myself. The first time was when I was lucid dreaming about persuing girls to have sex with. I asked a character in my dream where I could find some girls and the face of this person distorted in such a way to suggest to me that I was looking at a real demon. Of coarse I was extremely scared and forced myself awake.
The second time was during a lucid dream in which I was drifting in and out of sleep, and I was dreaming that I was walking through my house. During the times that I would briefly awake I really felt as though I was rushed back into my bed and into my body. Then at my bedside I saw a large and imposing figure which was composed of mostly bright light (he had no features). This being warned me about my wrongdoings in life and showed me what the end result was by inflicting upon me the feeling that my heart was being squeezed or constricted. I immediately forced myself awake.

Again, I do not have a truely solid stance on whether or not these people or beings which I interact with in a lucid dream are all myself or if I'm merely interpreting these beings to have a visually acceptable human appearance (as suggested by the man who said he was really a tree). I would like to know if anyone else has posed similar questions to people in lucid dreams.