In one of my first lucid dreams, I was going around through this park and trying to talk to people. Most people were just like zombies and ignored me. I would go up to them and ask them if they knew they were in a dream, and they would just look at me strange and walk away. One woman even pulled her children away from me. I eventually noticed this one man, who did not look like the others. He was leaning against a stone wall, and looking around perceptively. He wore a maroon polo shirt and tan khakis, the same as security guards at my school. I walked over and said, "You know we're in a dream, right?" He looked back briefly and said, "Yea, I know." I told him he was the first person to say that and kept on trying to talk to him about stuff in the dream. He said he was busy though, and when I asked him why he told me it was because he was looking for someone very important and dangerous.
I recently had this discussion in another forum. I remember finding a dream character in one of my dreams who had been there the whole time. I finally spoke to him because he was, as you said, more perceptive in his appearance than the others. When I would tell my DCs that they were in dreams, they wouldn't get angry or walk away or anything, they just wouldn't respond. For example, I "proved" that some of my DCs were DCs to them by having them look at my watch and how it didn't behave like a real watch should. They just stared at the watch and said nothing.
But I finally noticed this one man. When I asked who he was, he said that he was an angel (if I recall) and began to analyze and question many of my life decisions. It was quite interesting.