Visible crew/equipment: After Kirk tells the policeman that he wants to see Merikus and "perhaps" he's a friend, the policemen lock the cell then leave, and when it cuts to a view of the cell from the side as Spock walks over to the steel bars, the overhead boom mic is visible inside the cell, over Spock. It's visible again, with a better view, when McCoy walks over to Spock beside the bars. (00:18:15)
Revealing mistake: After being put in the cell, when the camera is in a closeup of Spock, you can see the lines in the prosthetic ears, and can easily tell where the makeup is blended into his real ear.
What Are Little Girls Made Of? - S1-E8
Revealing mistake: When Korby introduces the new android Kirk to Chapel, as the duplicator table slowly turns the edit in the footage can be seen in this shot, just as the real Kirk suddenly vanishes from the space he was in.
Let That Be Your Last Battlefield - S3-E15
Continuity mistake: The planet Cheron is blue the first two times we see it on the view screen, but when the Enterprise enters orbit, and every time we see it thereafter, the planet has mysteriously turned red. (00:44:05 - 00:46:00)
Continuity mistake: In Janice Rand's quarters, Charlie mentally throws Kirk and Spock against the wall. After they collide with it and slide down the face of the wall, there is a huge indention and crack where Spock hit. After a camera cut to Charlie, when the camera looks at Kirk and Spock again, there is no damage to the wall. (00:36:52)
Character mistake: Elaan says "If I have to stay here for ten light-years..." A light year is a measure of distance. (00:24:03)
Other mistake: While on Starbase 11, Kirk and McCoy watch Pike on a starbase desktop monitor as his light keeps blinking no. When Kirk is with Mendez in his office discussing the Talos IV top secret file, Piper watches Pike on the desktop monitor in the office. Then Spock uses the monitor in his quarters to watch Kirk. All these monitors have the same dings and markings around their screens, which are also the same as other desktop monitors on Enterprise in the previous episode, The Corbomite Maneuver. (00:11:10)
Where No Man Has Gone Before - S1-E4
Visible crew/equipment: While Kirk is armed with a phaser rifle he quietly moves closer to Gary and Dr. Dehner, but when Gary senses the "foolish man" he causes a boulder to roll past Kirk, and the arm of a crew member is visible behind the boulder pushing it forward. (00:39:40)
A Taste of Armageddon - S1-E24
Visible crew/equipment: When Mea 3 escorts Kirk and his landing party to Anan 7 and members of the High Council, while the group enters the room the actors' marks are visible on the black rug, as they all stand at their marks. (00:06:55)
Visible crew/equipment: When the Metron returns Kirk to the Enterprise he reappears on the bridge, and the actors' chalk marks are visible on the floor where Kirk and crew stand. (00:47:20)
Continuity mistake: After Sam tosses Kirk, he goes to a bench in the corner, picks up the towel that was there, and sits down. After Kirk tosses Charlie, Sam is laughing, and Charlie makes Sam "go away." After Sam fades out, the towel that he had around his neck is lying there, when it disappeared with Sam. (00:27:36)
Continuity mistake: Uhura starts to sing and walk around Spock as he plays. In Spock's close ups, the wall behind him is pink and green, but in the further shots the walls are a blue color with nothing behind him that could have been making the green and pink colors in the close ups. (00:10:50)
Continuity mistake: After Spock and Kirk attempt to trap Charlie into a room with a force field, Charlie makes the wall disappear and then freezes Kirk and Spock in place. Spock has his right hand against the wall at about chest level with himself. The camera cuts to a closer angle and suddenly his hand is higher up, about face level. (00:39:47)
Continuity mistake: When Kirk begins to question Charlie about the melted chess pieces, there is a close up of Kirk showing light cast down him him with his chest void of any shadows. When cut to a wide angle, he suddenly has shadows on his chest from lighting changes. (00:22:36)
Continuity mistake: Just before Uhura begins to hum with Spock's playing of his instrument, she is leaning over a table where they are playing cards. She has one hand on her cheek and then brings the other up to her face as well. When it cuts to a side angle, she's suddenly bringing her hand up to her face again in a repeated action. (00:09:47)
Revealing mistake: As Charlie watches the pole lowering into a square hole in the deck, the wood grain of the set piece is visible. The wood has been painted gray/silver to look like metal. (00:06:06)
The Man Trap - S1-E2
Continuity mistake: When Kirk is telling Crater that he needs him and his wife to stay on their ship till he finds out what killed his man, Kirk has his arms crossed. When Crater steps up to him and the angle changes, Kirk's arms are suddenly down at his side. This continuously changes back and forth between shots. (00:18:07)
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.
