Factual error: As Kirk, McKoy and Scottie age during the episode, their hair goes from brown to fully grey. Mr. Spock shows this to a lesser extent, but by the end of the episode, he has full streaks of grey. This isn't how grey hair works. It starts from the root and works it way outward over time to the end of the strand. Unless their hair is growing quite rapidly, and then cut to keep it short, they shouldn't have full heads of grey hair.
The Immunity Syndrome - S2-E18
Character mistake: The officer at the helm is referred to as Lt. Kyle, and is named that way in the end credits. Yet throughout the episode, Captain Kirk keeps calling him "Kowel".
Continuity mistake: In a wide shot of the Capellons and the Klingon walking down the hill, the Klingon trips and falls to the ground and picks himself up. Next shot, tight group with Klingon, he is suddenly brushing off his pants.
Suggested correction: After Kras falls, the next shot you see him still on the ground and starting to stand up, although Maab blocks the view of him. The shot cuts to the rocks and then when it cuts back, you see Kras walk up and stand next to Maab, then he starts to dust himself off.
Suggested correction: Why would he not be doing that in the next shot? There is no continuity issue.
Visible crew/equipment: The action is shifting back and forth from the bridge where the alien ship is attacking and sickbay where McCoy is operating on Sarek. In two separate takes when the scene shifts to sickbay McCoy is standing at the operating table. I noticed a wisp of smoke rising from McCoy's right side (left side of screen). It appears to be from a cigarette in an ash tray below camera level either beside McCoy or near the head of Spock's bed.
Suggested correction: This was an intended physical effect to simulate the cryogenic surgery that McCoy was performing on Sarek.
Who Mourns for Adonais? - S2-E2
Continuity mistake: In the original version, the giant hand is holding the Enterprise for most of the episode, but when the Enterprise fires phasers at Apollo's temple, the hand is gone.
Continuity mistake: After the heavy door lands on Korob, his right arm is straight down by his side. The next shot of Korob shows his right arm extended away from his body.
Audio problem: About a minute or two into the episode, Captain Kirk says "That's incredible" but his mouth doesn't match the words.
Continuity mistake: On the planet surface, in the scene where the three security men walk around the rock, Garrovick has his arm up with his phaser. When the camera angle cuts to him alone, his arm is suddenly down.
Continuity mistake: Gary Seven pushes a pen holder over to open the doors. The pen wasn't returned to the upright position, but was up when Kirk came in.
Continuity mistake: When the computer opens and begins operation in Gary Seven's office, it's white. In the close up, it goes from white to purple when asking for identification. Afterwards, the color continues to change.
The Immunity Syndrome - S2-E18
Continuity mistake: At the shuttle craft deck, Spock is standing on the same side of the door as McCoy, then moves to the other side. When McCoy looks at Spock, he is standing on McCoy's side of the door again, then is back on the other side when the door opens.
Continuity mistake: Spock is standing in the background with his back to the wall and his hands behind him. A few seconds later, the shot changes to him deep in the "Plak Tow", with his left shoulder touching the wall and with his hands intertwined. The next shot has him standing with his back against the wall again, hands behind his back again. The scene would have flowed nicely if they hadn't inserted the "Plak Tow" shot in between. That two second clip had been used already a few minutes earlier. (00:33:03)
The Ultimate Computer - S2-E24
Visible crew/equipment: After M-5 fires on the other starships Daystrom speaks to M-5 about the murders, then when Kirk walks over to Daystrom and tells him the M-5 must be destroyed, the shadow of the moving boom mic is visible over Daystrom. The white tape mark is also visible on the floor near Uhura's chair, where McCoy had been standing earlier. (00:42:15)
Continuity mistake: While Kirk, Spock, and McCoy attempt to escape, Merik contacts Enterprise with the stolen communicator and the Proconsul stabs him, then when Merik tosses the communicator it lands in front of Kirk's feet in a closeup. The problem is that in the closeup Kirk is wearing his black uniform pants, but during this scene Kirk is wearing the light colored slave pants. Also interesting to note, when the sword landed on the floor in front of Spock's feet, the Vulcan is wearing black lace-up flat footwear instead of his black uniform boots. (00:46:35)
Revealing mistake: After Scotty finally locates Seven on the gantry while he's tampering with the rocket, it cuts to a quick shot of Kirk and Spock, then in the following shot of Roberta when she turns the vault's combination locks, the stunt wire is visible behind her as it moves up to turn the door's wheel handle. (00:35:25)
The Ultimate Computer - S2-E24
Continuity mistake: During the scene with the ore freighter, there are four closeups of Spock while he's bent over the scope at his station, and in the background behind Spock we can see Kirk and others on the bridge are gone. It also occurs in the earlier scene during the encounter with the two starships. (00:24:00)
Visible crew/equipment: After Melakon shoots at the curtained window and kills John Gill in the broadcast booth, Isak shoots Melakon, then when Eneg stops the soldier who points his gun at Isak, the shadow of the boom mic dips into view at the top, left side of the screen. (00:45:50)
Deliberate mistake: When Rojan asks Kelinda if she wishes to remain with Kirk, she replies that although Kirk is "most interesting" she wishes to go with him, and the next closeup of Rojan is flipped. (00:48:15)
