The Morlocks and the Eloi originally came from H. G. Wells' book The Time Machine. In it, the narrator travels into a future in which the human race has diverged into a cave-dwelling, machine-operating servant race and a carefree, happy, and rather stupid race of dainty surface-dwellers called the Eloi.

Only, the narrator had arrived not too long after the Morlocks started killing the Eloi.
Go read the node, Orange Julius has put the entire book in everything.