Visible crew/equipment: While Spock and McCoy are discussing the dangers of the experimental drug, when McCoy tells Spock that he can't sanction it, the two white tape marks are visible on the floor. (00:26:30)
Visible crew/equipment: While Sarek is lying in sickbay, McCoy, Spock, and Kirk discuss the open heart procedure, and when Christine walks over to stand beside Sarek, the white tape mark is visible on the floor where she stands. (00:24:20)
Visible crew/equipment: When Kirk walks into the brig Spock tells him that Nomad has almost human stubbornness, and that its screens are still up, then just as Kirk moves closer to Nomad the shadow of the moving boom mic is visible at the top, left side of the screen. (00:28:15)
The Trouble With Tribbles - S2-E15
Visible crew/equipment: After Mr. Baris takes Darvin into custody and leaves the room, when Kirk walks over to Captain Koloth three white tape marks are visible on the floor. (00:45:10)
Visible crew/equipment: A stagehand's foot is visible before the party beams down. (00:09:10)
Visible crew/equipment: As the camera swings around to simulate the crewman's gaze, the top of the background is visible for a second until the camera pans down.
Visible crew/equipment: As the camera looks at the Galileo, if you look at the green background, you can see the top of the sound stage.
Visible crew/equipment: As Kirk goes to talk to Uhura, the studio light is reflected of the second to left panel from Uhura.
Visible crew/equipment: The shadow of a boom mic is seen against the rock walls of the cave follows Spock and McCoy when Spock pulls McCoy off Zarabeth.
Visible crew/equipment: Set lights are reflected in Spock's tricorder screen before he closes the cover.
Mudd's Women - S1-E7
Visible crew/equipment: In the briefing room, as the camera moves to its left along the seated figures, the camera rig is reflected in the glass of the communication view screen.
Where No Man Has Gone Before - S1-E4
Visible crew/equipment: As the camera is close up on Kirk, and as he addresses the ship, the shadow of the boom mic plays on Smith's neck. (00:04:35)
Visible crew/equipment: When the camera looks at Spock after Scott's body is removed from the bridge, the shadows of lighting equipment is visible behind him.
A Piece of the Action - S2-E17
Visible crew/equipment: As Kirk comes around the front of the car in front of Krako's headquarters, another boom mic is reflected on the fender.
A Piece of the Action - S2-E17
Visible crew/equipment: As Kirk first drives the car, the camera is reflected in the car's chromed radiator.
The Gamesters of Triskelion - S2-E16
Visible crew/equipment: As Ensign Haines reports to Spock, the shadow of the camera mostly shades her, then it plays over McCoy.
Tomorrow is Yesterday - S1-E20
Visible crew/equipment: When Kirk hears the audio for the first manned moon shot, he gets up to walk over to Spock. As the camera pans to follow, the shadow of the boom mic can be seen moving quickly above and to the left of his head.
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.