This Side of Paradise - S1-E25
Other mistake: After Spock is hit with the spores, he goes down on all fours in pain. As he writhes around, the skin tone of his ears is vastly different to his other makeup.
This Side of Paradise - S1-E25
Other mistake: As Spock and Kirk are fighting, Spock bends a steel bar with one of his blows. When he hits Kirk, though, it simply makes Kirk a little sore. A blow strong enough to bend a steel bar would shatter human bones.
Answer: Kirk was getting his physical and Dr. McCoy probably turned off communications, because if he hadn't, Kirk would have left and headed straight for the bridge, leaving McCoy irritated.