Star Trek: 9 Times Mr. Spock Got A Power-Up
3. The F.S.N.P.
Originally, the script for “The Enemy Within” called for Spock to subdue the "duplicate" Kirk via rather violent means:
The double starts to fire when, abruptly, Spock lunges out from behind one of the generators and kayoes the double. The double's phaser beam (ANIMATION) strikes some apparatus across the way as the double falls BELOW FRAME. After several moments, Kirk comes INTO FRAME and in silence, looks down at "himself". CAMERA PANS DOWN toward the double... in this angle we can now see some of the destroyed machinery.
But actor Leonard Nimoy protested that such violent action was out of character for Spock. Reportedly, he huddled with William Shatner and they improvised a bit of business wherein Nimoy grabbed Shatner’s shoulder in an odd way and Shatner rolled his eyes back and collapsed. The director went for it, and the F.S.N.P. (Famous Spock Neck Pinch) was born. But this bit of improv was not initially met with cheers because just three weeks earlier a memo from Trek creator Gene Roddenberry to "All Concerned" had cautioned against such on-set improvisation:
Cameraman and script supervisor have been alerted to flash this office should the director depart appreciably from dialogue, characterization, etc.
A few months later, the subject got raised again in a letter from Gene Roddenberry to several members of the production and cast—including Nimoy—dated September 14, 1966, which included this:
On a couple of the preceding shows, due to our production staff being deeply involved in post-production problems, it was necessary to make a number of script dialogue and action changes on set. And we appreciate the hard work you and others did in accomplishing this. However, obviously none of us want this to become a habit since it is precisely this type of thing which has destroyed the format and continuity of more than one television series.
The time and pressure everyone on set is undergoing during actual photography does not permit the kind of in-depth analysis of scenes which is necessary when such changes are to be made. Most often, as you are well aware, they may seem to improve the specific scene being shot but create difficulties and surprises in the cutting room later when it is suddenly realized that key information (seemingly unimportant at the time) has been lost.
So Nimoy got scolded but Spock got powered-up.