Star Trek (1966)

The Enterprise Incident - S3-E2

Plot hole: In the conference room, Spock informs Kirk that his theory of a Romulan cloaking device kept the sensors from detecting the ships. However, in S1:E14, "Balance of Terror", they figured out the cloaking device, and how it worked. Unless he was feeding into the deception, Spock shouldn't have had any theory when it was a fact.

Movie Nut

The Enterprise Incident - S3-E2

Plot hole: Despite the Romulan ships keeping a close watch on the Enterprise, when they beam the disguised Cpt Kirk over to the Romulan vessel it goes undetected.

olohzika

The Paradise Syndrome - S3-E3

Plot hole: If diverting the asteroid was so important, what was the crew doing on the planet to begin with?

hifijohn

Is There in Truth No Beauty? - S3-E5

Plot hole: When the Medusan Ambassador Kollos and Dr. Jones materialize, the latter is wearing a protective visor and Mr. Spock can see that. Spock then mistakenly addresses Dr. Jones as Ambassador Kollos. Spock's suddenly illogical mistake seems odd: why should the Ambassador need to wear a visor? Shortly after, why do both Jones and Spock wear visors while carrying the Ambassador's still closed gasket to his cabin? (00:01:45)

For the World is Hollow and I Have Touched the Sky - S3-E8

Plot hole: Spock says the spaceship asteroid will collide with Daren 5 in 396 days, but without knowing the exact location of Daren 5 at that moment it would be impossible to predict a collision.

hifijohn

Wink of an Eye - S3-E11

Plot hole: Spock plays back a tape of Kirk, McCoy and Compton on the surface of Scallos that no one in the landing party could have recorded. What a coincidence that it's identical to the footage that opened the episode. (00:36:05)

Jean G

The Empath - S3-E12

Plot hole: Spock calculates that it will take 72 hours for the solar flare to pass, and Kirk orders the Enterprise out of the area. 3 days is a long time to go without food or water, and as the station is deserted as far as they know, there'd be no way to supply themselves, but the Enterprise leaves without a second thought.

hifijohn

All Our Yesterdays - S3-E23

Plot hole: The law officer who arrests Kirk recalls hearing Kirk call the "spirit" Bones. But he wasn't there when Kirk spoke to McCoy. He rushed into the scene several minutes later. If he's lying, how would he know that Kirk used the name Bones? He wasn't there to hear it. Even if he had been, Kirk did not refer to McCoy as Bones in that conversation. (00:10:50 - 00:19:50)

Jean G

All Our Yesterdays - S3-E23

Plot hole: Spock's phaser doesn't work because they are in a time when phasers didn't exist, but McCoy's tricorder does.

hifijohn