Corrected entry: Mr. Flint grabs the Enterprise out of orbit and transfers it onto the table. We assume, because the ship is small, it doesn't weigh much. However, Star Trek canon states the Enterprise weighs 190,000 metric tons, size not withstanding. There's no way that small table could hold such a massive weight.
Corrected entry: Spock is wearing his normal blue uniform when shot with the "happy spores" from the strange plant. The next scene is with Kirk inquiring about Spock's location to which he is told nobody has seen him. Spock somehow manages to find some green overalls out in the meadows when we switch back to him. (00:17:40)
Corrected entry: In a very strange coincidence, a little more than seven minutes into this episode, which aired March 29, 1968, Spock states there will be a major assassination today. Six days after the original airing, Martin Luther King was assassinated in Memphis on April 4, 1968.
Corrected entry: When the Enterprise is slingshotting its way back to the "present" it uses the computer to deposit the two men at different times, The Enterprise is traveling backwards in time, so will logically meet the time when the guard was beamed up first, not after Christopher is returned to his cockpit. So the order is wrong. Should be guard then Christopher, not Christopher then guard. (00:43:15)
Corrected entry: If the point was to repair the ship, and maroon Gary Mitchell, then why have Lee Kelso wire a destruct button, thereby threatening Gary's life and placing Lee's life in jeopardy when Gary's powers could overcome him? If they were afraid Gary would become too powerful left on his own, then marooning him should not have been an option.
Corrected entry: After Kirk and Spock's identities are revealed, they are taken to a prison cell. However, the Organians are a race of pacifists who abhor any act of violence - this should presumably include the act of incarceration. As such, there should be no prisons on Organia. Moreover, the Klingons are not stone masons; the prison cell shown in the episode is architecturally consistent with the other buildings on the planet so it was not constructed by Klingons (especially so quickly).
Corrected entry: In the credits, Joan Collins' character is named "Sister Edith Keeler." But her character is engaging in a romantic/sexual relationship with Kirk. He says he has "ulterior motives" towards her which she reacts to playfully and kisses him. Not appropriate behaviour for a sister, particularly in the time and place the episode is set.
Corrected entry: Just how the Troglyte spy manages to leap over one of the cloud city's balconies to his death is a bit puzzling. Stratos City is held aloft by huge anti-gravity generators. An anti-grav field should, sensibly, extend far enough past the balcony railings to keep people from falling off. Surely the self-obsessed Stratos dwellers would extend that field, since they want to protect their own skins above all else. (00:07:05 - 00:11:30)