the cost of production was immense, partly because of the special optical effects needed to matte the little people into shots also showing the giants; and partly because of the gigantic mechanical props needed, for the little people to interact with, in shots depicting the giant-sized world they find themselves in; plus the futuristic spacecraft sets that were needed to represent the "spindrift". because of the enormous cost, it was more efficient and cost-effective to film episodes in pairs using the same sets; so writers were informed about what giant-size props there were available, which they could incorporate into their storylines. these episodes were filmed back-to-back.