Continuity mistake: As Kirk and Spock head towards the Only, they first approach him from the same side. When the camera cuts to a different angle, they are approaching from different sides. (00:05:09)
The City on the Edge of Forever - S1-E29
Factual error: The song "Goodnight Sweetheart" was written and first performed in 1931. This episode takes place in 1930, one year before.
Tomorrow is Yesterday - S1-E20
Character mistake: Kirk introduces Spock as "Lieutenant Commander Spock," but Spock is obviously wearing full commander's stripes on his uniform.
The Conscience of the King - S1-E14
Continuity mistake: When Spock explains to McCoy his theory of Kodos' use of eugenics, the background behind Spock is a wall of red grating, but the shots of Spock speaking to McCoy alone (McCoy isn't in the shot) show a blue background wall with a control panel on it. (00:21:55)
The Conscience of the King - S1-E14
Continuity mistake: As Kirk asks the Enterprise's computer about the history of Anton the Actor and Kodos the Executioner, his hands change positions from being away from the computer's controls to near them, then clasped as the shots quick cut.
Continuity mistake: When the Enterprise tries to escape Gothos, and the planet blocks the ship's path each time, Gothos is very transparent, where the stars could be seen through the planet.
A Taste of Armageddon - S1-E24
Continuity mistake: At the end of the teaser, Kirk orders Yellow Alert, but the Red Alert alarm sounds.
The Alternative Factor - S1-E28
Other mistake: When Spock calls Kirk to the bridge after he discovers the Lazarus energy source, he and Lazarus head to the bridge. There is a shot of McCoy standing in the corridor, and one of the red alert panels is burned out while the other is still flashing.
Other mistake: In the Briefing Room, while Kirk is feeling the effects of the disease, Spock tells Scotty that he will call the restart formula in from the bridge. But just a moment later, Kirk enters the Bridge, and Spock is in the Engine Room working on the settings and formula with Scotty.
The Conscience of the King - S1-E14
Revealing mistake: As Kirk and Lenore leave the cocktail party to walk around outside, they stop to talk. From Kirk's perspective, he is to the left of Lenore, enough to see what should be in view ahead of him. Only seconds later when she leans in to kiss him does he notice Dr. Leighton lying next to some rocks. She was not obscuring his view before. Why didn't Kirk see this while they first started talking? (00:10:36)
Shore Leave - S1-E16
Revealing mistake: After Rodriguez and Angela run from the strafing plane, they end up stopping next to a tree. Angela falls to the ground without Rodriguez knowing that she was hit by the gunfire. He continues to watch the plane disappear with his head looking upwards. When his head comes back down, rather than looking towards her to talk (where her face would be if she was standing), his eyes immediately look down at her on the ground...as if he'd been expecting that she'd be lying there all along. (00:34:01)
Other mistake: Kirk orders the helm to get phasers ready to fire at the Romulan vessel. When the helm responds, it's not the phaser banks that fire, but photon torpedoes. (00:32:58)
Continuity mistake: After the battle ends, Kirk looks up to the exact spot where the Metron will be standing, way before the Metron even materializes. (00:45:53)
Continuity mistake: After Kirk tells the Metrons that he won't kill the Gorn, he yells out "you'll have to get your entertainment someplace else." Two seconds later, Kirk turns his head to the side and looks stunned. That look of surprise takes place a full second before the Gorn starts to disappear. (00:45:47)
Space Seed - S1-E23
Other mistake: Spock calls for McGivers and Scotty to the transporter room. In the Transporter Room, Scotty is at the controls, then after he went to the Transporter pad, they used a stock shot of his hands working the controls.
Revealing mistake: When first seen on Gothos, the "frozen" Kirk's eyes blink.
Space Seed - S1-E23
Revealing mistake: During the fight sequence between Kirk and Khan in the engine room, you can see in some shots that it is not William Shatner and Ricardo Montalban fighting, but their stunt doubles.
Space Seed - S1-E23
Visible crew/equipment: When Khan hides behind the wall in the engine room before Kirk enters, a crew member walks in front of the stage light and you can see the shadow of his head passing across the floor.
Shore Leave - S1-E16
Revealing mistake: When Yeoman Barrow places her tunic on a shrub while changing, automobiles can be seen in the background through the brush.
Continuity mistake: Latimer falls down face down but when picked up he is already face up.
Answer: After causing Norman to overload, all of the other androids shut down. The same could be said for the androids on the Enterprise.