do you ever think about someone, and in your mind, you see them so clearly?

Sometimes its like my subconscious mind flashes images of people into my conciousness, and it's so weird, because I feel like i wasnt even think about them. But when that happens, it's like, I can see their face, so clearly in my mind. Does anyone else do that? It almost feels like I'm surrounded by their presense, when I know they aren't actually there... it kind of freaks me out.