My contribution to that imagery was in 1979 with this book [Messengers of Deception: UFO Contacts and Cults (Ronin, June 1979)] cover [shown at top].
At the time, I instructed the artist to show a human walking deliberately away from a hovering saucer rather than running away or cowering in front of it.
Most readers at the time didn't like the image, too disturbing and not in line with expectations about flying saucers: the occupants shouldn't be human.
I think what was disturbing in the 'Messengers' image was the implication that some humans knew what the saucers were, and [the 'others'] were walking quietly into our world.
The French scientist Claude LaCombe in the Steven Spielberg film Close Encounters of the Third Kind was based on my friend Jacques Vallée.
My Boing Boing buddy David Pescovitz mentioned the following magnifique deleted scene from the film that says some things about twilight language:
David Laughlin (Bob Balaban). Name game note: Laughlin, Nevada, in the extreme southern tip of the state, has become a modern focal meeting point for ufology conferences, anomalistic gatherings, and Area 51 researchers.
See here for more from David Pescovitz on what special phrase shows up in CEIII that is, indeed, so very Vallée.
Thanks also to Patrick Huyghe of Anomalist Books for bringing the deleted scene to my attention in 2009.