OP,

I would call what you are describing in your dreams as "dream scouts". They always appear as something quite vivid, and quite out of place. My examples are: a floating (in mid air) rainbow colored angelfish, a metallic green clown shoe on my left foot, an antique umbrella made of purple crystals, a talking dog who looked like a rhino-face and babbled incoherently, a breathtaking woman with dazzling green eyes that appeared to have spirals in the irises. In all cases, the dreams were quite vivid, familiar yet surreal. In most cases they take place in scenarios that I am "familiar" with, like a childhood home or neighborhood, and yet, although in the dream I am convinced I know the place well, upon waking, the details don't even come close to the place that I believed I was in (the school was nothing like my old school...the house nothing like my old house...the neighborhood not even close to the layout of my old neighborhood), but during the dream, everything is exactly where I expect it to be, and in its "proper perspective".

I have come to learn that dream scouts do this, for their own reasons, often to elicit an emotional discharge. I am perhaps not the best person to discuss them, but there was once a book that did a decent job of describing it (yeah here i go again with the castenada crap...) The Art of Dreaming by Carlos Castenada. Keep in mind that this is one of his latter works, possibly his 10th or 11th book even (not sure to be honest). The book is quite detailed, and if you want to understand what and why, I'd suggest giving it a read. I'm sure it will captivate you from the introduction itself (which you really should read as it's somewhat of a recap of previous books, and a description about how we perceive reality).

Dream Well!