Neolithic Nightmare / The Return of Brainiac

S1 E6: Jimmy Olsen falls into an underground pocket populated by malevolent creatures. An alien computer named Brainiac has been capturing different kinds of animals by shrinking them. Brainiac is taking the tiny animals to his dying home world on his spaceship a la Noah's Ark. When he also must find a man and woman for repopulation, Brainiac ends up shrinking and capturing Superman and Lois.