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.
Continuity mistake: As Kirk and party dematerialize, Kirk's arms are by his side. As they are briefly seen in the Transporter room, his left hand is up with the communicator.
Who Mourns for Adonais? - S2-E2
Other mistake: The bushes behind the temple shimmer in time with the temple when the ship is firing on it, but they aren't connected to it.
Who Mourns for Adonais? - S2-E2
Audio problem: At the temple, as Kirk goes to call the ship, he flips the communicator to open it, as he usually does. However, he has to flip it twice to get it to open, but the sound of the channel opening is heard from the second he starts.
Who Mourns for Adonais? - S2-E2
Revealing mistake: As Apollo's head and neck appear on the screen, the neck of the black T-shirt used to mask his body is easily seen, and his shoulders are faintly visible.
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
Revealing mistake: As Kirk and Spock take off in the car, the painted backdrop is recognizable between the buildings. There is a vertical edge to it about three feet away from the edge of the auto repair building.
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.
The Trouble With Tribbles - S2-E15
Continuity mistake: After Kirk opens the bin, the Tribbles fall on him. At first, he shields his head, then drops his right arm. Suddenly, it's over his head again.
The Trouble With Tribbles - S2-E15
Continuity mistake: During the brawl, as Cyrano Jones watches the action, the glass he quickly raises loses most of the liquid. After he gets half way through the scene, the glass is suddenly almost full.
The Trouble With Tribbles - S2-E15
Continuity mistake: Uhura's image on the conference viewer is of a close up on her face. When the camera looks at the screen, the image is of her head and upper torso. Likewise, when Fitzpatrick is on, first it's his head and torso, then it's only his head and shoulders.
Factual error: Kirk, McCoy, and Spock are chained to the dungeon wall, with McCoy noticing he is next to a skeleton, also chained. This is incorrect, as a skeleton's bones are held together by cartilage, which would rot over time. Therefore, the skeleton would not be hanging intact, but would be a pile of bones on the floor.
Suggested correction: As we learn in the episode, the 2 aliens created the entire castle only recently to appeal to the human's primal fears and superstitions. A pile of bones on the floor would not have the frightening impact of a hanging skeleton.
Audio problem: As Commodore Stocker freezes up on the bridge, before the cut to sick bay, the bridge is shaken by a Romulan blast, but the sound is absent.
The Ultimate Computer - S2-E24
Continuity mistake: When Sulu is first reporting the M-5 movements, Kirk's hand alternates between being up at his temple and down by his mouth, too quickly to be real.
Revealing mistake: In the close up shots of the mirror Sulu, the poor make up job of the scar on his face is very evident.
Continuity mistake: When Kirk and Spock get to Sick Bay, the doors open to reveal Nomad coming out. But the shot of Nomad coming out is a re-used shot of it coming out of the Turbo Lift, not the Sick Bay, as the nameplate said. (00:42:10)
Other mistake: Early on, there is a shot of the control room. There is a read out that is counting down from "5 04 15", meaning that the launch would be in just over five hours, not less than one minute.
Continuity mistake: The shots of the rocket Scotty cycles through are of different times. There is one shot of the rocket at the launch site, followed by one of the transport taking the rocket to the site.