Quotes
Scotty: On Earth, we have a saying: Fool me once, shame on you. Fool me twice, shame on me.
Chekov: I know this saying. It was invented in Russia.
Trivia
Many of the "onlies" in the final scenes of this episode were the children of Star Trek's cast and crew. They included William Shatner's two young daughters, Leslie and Lisabeth Shatner. See more...
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Star Trek (1966) - 304 mistakes in entire show
starring DeForest Kelley, George Takei, James Doohan, Leonard Nimoy, Nichelle Nichols, Walter Koenig, William Shatner (add more)
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Factual error: If Miri's planet is a "duplicate" (meaning identical) Earth, it should have clouds. It doesn't. This remains a mistake because "duplicate" means "exactly the same," and thus the clouds should be there. The special effects crew forgot to put them in. Noteworthy: the very first thing fixed in the digitally enhanced version of this episode was the duplicate Earth. It has clouds now.
Continuity: As Balok's 10 minutes are counting down, McCoy comes onto the bridge wearing a standard blue velour uniform. A few minutes later, when Spock says he can bring up Balok's image, McCoy is suddenly wearing his medical tunic with the different fabric and collar. Then when Bailey starts losing it, McCoy is back in the regular velour costume again.







