i was just reminded of an old series of sci fi novels i had read a long time ago. Basic plot was that all dissipeared/lost people were actually abducted by aliens. The aliens took their brains and put them in robot bodies for multiple purposes because the human brain was a good processer. they even did this to cats/dogs. Eventually a guy breaks out of the control to find his brain in a robot body at a junkyard. Eventually he finds that he can kinda wake others and eventually frees the minds of some other robots, one actually being a viking. then of course the rebelling against the aliens. does this seem familiar to anyone? i cant remember anything else other than this.

Never heard of it!

Sounds like A Plague of Demons, by Keith Laumer. A very enjoyable story which seems to have inspired his Bolo series.