On Feb. 16, 1967, Star Trek fans met possibly the most convincing villain of the entire franchise when the first-season episode “Space Seed” aired.

The USS Enterprise encountered a drifting ship, seemingly at least 200 years old, with confusing life signs detected within. Beaming across, Captain Kirk and his party discovered a crew of 84 humans in suspended animation, all but 12 of whom remained alive. Kirk rescued the leader from his failing life-support unit, and Khan Noonien Singh made his first impression in Gene Roddenberry’s universe.

Seeking at first to hide his identity, one of Khan’s first acts was to threaten the life of Dr. McCoy. Suspicions aroused, Kirk and Spock established that Khan was the leader of a genetically modified race of humans that ruled a large part of the world as a dictatorship during the eugenics wars of the 1990s, then escaped their fate on their sleeper ship, the Botany Bay.

After coming close to killing Kirk and briefly taking command of the Enterprise, Khan was finally captured and a trial was held aboard the ship. Kirk decided on leniency, offering Khan the chance to build a new society on an uninhabited planet. Agreeing to take historian Lt. Marla McGivers with him after she’d fallen under his spell and tried to help him steal the Enterprise, Khan accepted the offer by referring to a John Milton line: “Better to reign in Hell, than serve in Heav’n.” As the war criminal left to begin a new life, Spock observed, “It would be interesting, Captain, to return to that world in 100 years and learn what crop had sprung from the seed you planted today.” Kirk replied: “Yes, Mr. Spock, it would indeed.”

Watch Khan Threaten McCoy on 'Star Trek'

The episode rates highly among fans and critics, and Ricardo Montalban’s performance as Khan retains a sharp tone all these years later. It does have its flaws, notably the way McGivers is depicted as a pushover for Khan, the fact that super-intelligent advanced humans can take over a starship but don’t know how to operate a viewscreen and the fight scene between Kirk and Khan where the stunt doubles’ faces are visible.

But in other terms, it delivers strongly. The respect shown between Kirk and Khan is notable, as is the development of the Kirk-Spock relationship, especially when the Vulcan expresses amazement that his shipmates admire their enemy and to be told by Kirk that humans “have a streak of barbarism in us,” whether they like it or not. It’s also the first episode where Scotty, played by James Doohan, began to become a main character in the show.

Watch Khan Argue With Spock on 'Star Trek'

“I don’t know how I was cast, except at that time they knew I had a fairly good physique,” Montalban said later, adding that there was a requirement for someone who had “proven he could act” but also had the appearance of a superman. He added that it was essential for him to understand the intent of writers Gene L. Coon and Carey Wilber - namely that Khan’s mission was “to conquer the Enterprise and rule the world.” “One of the most difficult things for an actor to do is what we call exposition – setting the stage … you have to use [your] humor, energy, inventiveness so that people don’t go [yawn]. And for seven years all I did on Fantasy Island was exposition. Setting the stage for somebody else. … There was never any emotion. That’s why, when I did Khan, I was able to really put the emotion out there!”

His emotion was so effective that, 15 years later, Montalban was invited to play the character again in Star Trek II: The Wrath of Khan, which is generally regarded as the best of the original cast movies. “They went through all the villains,” Montalban recalled, explaining that after the mixed response to Star Trek: The Motion Picture, the producers knew they needed an enemy with more character than a computer. “When they came to mine, they said, ‘Wait a minute. It would be interesting to see what happened to him on that planet.’”

It was indeed, to the extent that it’s arguable that Star Trek could have permanently ended if the return of Khan wasn't such a success. The character returned in 2013’s Star Trek Into Darkness – played by Benedict Cumberbatch this time – and he’s been referred to in several spin-off series.

Watch Khan and Kirk Fight It Out on 'Star Trek'

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