I had a dream once when I was younger. It was a very lucid and realistic dream about a life form that was found on the moon. Imagine if you will, a worm-like creature, perhaps between one and two feet long. It's body was stout - podgy - and segmented. It's mouth was a three-lipped and within it were several rows of teeth all the way around. If you're thinking of the film Dune, you are very close to how these worms appeared, except the obvious difference in magnitude.
This worm resided only a few centimetres beneath the surface of the moon and seemingly never needed to come up to the surface. It was only when astronauts, after landing on the moon, began to dig for dust samples that they discovered these unusual beasts.
Further investigation revealed that these worms also lived on Earth. Somehow, they had managed to colonise the moon. It was supposed that a heavy asteroid impact might have blasted a portion of the Earth towards the moon eons ago, seeding the rocky satellite with these amazing creatures.
This is the kind of thing I used to dream about.