Carlos Castaneda and the Grey Alien Allies - The First Extraterrestrial Conversation?
If you look into the Nagual vs Tonal part of Castaneda's work, you can clearly see he is discussing what science has come to term the left and right hand sides of the Brain. You can look at Jill Bolte Taylor's talk on YouTube at Ted to get an idea of the difference between the two worlds, but essentially one is held together by dialog and the other is rather like being a conduit for perception rather than processing or labelling.
Once you accept these two states/worlds then you can begin to accept that the allies of which Castaneda speaks (the inorganic beings) could well be the grey aliens as they are thought to be non-biological entities created by a race that may well have become extinct since, and that they emulate a human being, but because they are essentially soulless, they do not appear as a luminous egg, but as a human form, even in the world of the Nagual, or unrestricted non-verbalised world of the other half of the brain.