 Montalbán was the casting director 's first choice for Khan and described the role as " wonderful " . Despite being planned as an inexpensive bottle episode , the special sets and shots using starship miniatures caused the episode to go over budget . On first broadcast , the episode held second place in the ratings for the first half @-@ hour with 13 @.@ 12 million viewers , but during the second half it was pushed into third place . " Space Seed " has been named one of the best episodes of the series by Cinefantastique , IGN , and other publications . The 1982 film Star Trek II : The Wrath of Khan serves as a sequel to this episode . Plot elements of the episode and The Wrath of Khan were also used in the 2013 film Star Trek Into Darkness , and references to it appear in episodes of Star Trek : Enterprise . 
