Revealing mistake: When Kirk holds a golden egg, a seam can be seen on it. (00:43:55)
Space Seed - S1-E23
Continuity mistake: As the away team observes Khan in the stasis chamber, McCoy holds his tricorder with both hands, but the next shot shows him holding it in one hand.
Space Seed - S1-E23
Continuity mistake: On the Botany Bay, McCoy is not holding his tricorder, but when the ship's lights activate, McCoy suddenly has his tricorder in his hands.
Space Seed - S1-E23
Continuity mistake: When Khan asks Kirk "How long?" Kirk's head is near Khan's with nobody behind his head, but the next long shot shows Scotty behind Khan.
Space Seed - S1-E23
Continuity mistake: Khan's hands switch positions several times on the table between quick cuts as he and Kirk talk.
Revealing mistake: As Kirk and the Gorn battle, they briefly confront each other from opposite sides of a dead tree which has truncated limbs. One of the larger tree limbs on this supposedly uninhabited, tiny world has obviously been cut off with a chain saw or similar cutting instrument.
Revealing mistake: The stuntman playing Latimer is obvious when he falls after being hit in his back with the creature's spear.
Continuity mistake: As Veena (as the Orion Slave Girl) dances, the water in the pool is still, then in the Observation room, as Kirk and party watch, the water is disturbed. A moment later, it's flat calm.
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.
Other mistake: As Kirk and party duel against the Klingons, there's a heavy-looking round conduit on the wall right before the turbolift door that gets knocked down so it stands as a big flower pot. A moment later, it's back in position.
Continuity mistake: The first time we see the ship travelling at Warp Nine, it is moving in a level, straight path. Next time, the rear end is elevated above the line of flight. The next time, it's moving in level flight again.
Audio problem: The bartender comes over and brings whiskey and five glasses, but we hear six glasses hit the table.
Revealing mistake: During the televised fight, in the wide angle shots, you can tell it's Spock's stunt double fighting.
The Empath - S3-E12
Revealing mistake: When the Vian fires his weapon at Kirk after the crew finds Gem, Kirk flies backwards. At this point, Kirk is not William Shatner but a stunt double.
Continuity mistake: As Gary Seven starts to talk to the computer, it has a light gray exterior. When it first talks, the trim turns purple, then it's back to light gray.
Character mistake: When Kirk turns to face Spock and McCoy to introduce them to Sarek, the hangar deck nameplate on the wall is misspelled. It reads "hanger deck".
The City on the Edge of Forever - S1-E29
Continuity mistake: When trying to catch McCoy, Kirk's pants get dirtied. After coming out of the Guardian's time portal in the Depression, his pants are clean.
Character mistake: Mr Seven calls the security guard "Sergeant" but he is a corporal.
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.