|You know it makes sense|
Some Star Trek episodes are better than others. Some of the not-so-good ones, however, include good bits, which often stand out in the memory.
About "memorable bits". Before the days of video tape, the only way to see a TV programme was to be in front of a TV when it was broadcast. If you had to be somewhere else you were out of luck. Interruptions meant you missed something (no pause!) In many cases, this meant it could be years, if ever, before you had a chance to see something again. Some bits would stand out in the memory, even though you were vague about the rest.
Incidentally this is one of the reasons TV of the vintage of Star Trek TOS is often more episodic and less into "story arcs" than much modern TV.
"The Omega Glory" (TOS)
At the climax, Kirk and the renegade Captain Tracey fight. Meanwhile, Spock fixes his gaze on a woman and hypnotically causes her to pick up a communicator and bring it to him, so that help can be summoned. The view shifts between the intense fight, with a heavy drumbeat background music, and the eyes of Spock and the woman, with the fight music softened and a high tingling note. She walks across, very slowly. And, as the fight music begins to build again, she looks down at the communicator, and opens it. It chirps...
In context, this is one of the most exciting moments in TOS. In the middle of the violence, Spock is silently summoning help. And the climactic moment is just a communicator chirping.
(Side comment. There's a slight family resemblance to the "stealing the Enterprise" scene in the film Star Trek III—an exciting scene created by simply backing a starship out of a space station very slowly.)
"Spock's Brain" (TOS)
When the ship they are pursuing disappears into the Sigma Draconis system, they don't know which planet to go to. So Kirk asks for recommendations. It's a rare scene in which the bridge crew offer their analyses. Uhura doesn't make a recommendation but instead asks the crucial question, why would they want a brain? Then Kirk decides. The discussion is calm, respectful, and unhurried. It's a very satisfying little scene of the bridge crew working together, which people often seem to remember more than the episode it comes from.
Incidentally, although this episode is often listed as the worst in TOS, I think there is more to be said (see page on Spock's Brain)
"Starship Mine" (TNG)
Many people would dispute the inclusion of this as a weak episode. If you like this sort of action plot, it has merit, with the lethal "baryon sweep" moving slowly through the ship. My problem with it is that the story has almost no Star Trek significance: it doesn't seem to have anything to do with any of the themes of Star Trek, or indeed anything else much except the fight.
But, as the solipsist said, that's just one person's opinion.
Anyway, the good bit. In the early part of the episode, Data decides to learn how to "fill a silent moment with non-relevant conversation"—small talk. Picard advises him to study Commander Hutchinson ("Hutch"), who is a master of the art. At a social function, we see Data observing and practising Hutch's gestures and mannerisms, and then joining him in a small-talk duet. Brent Spiner, who plays Data, has great comedic talent, which here gets a chance to cut loose.
"The Outrageous Okona" (TNG)
This isn't really a bad episode, but it's run-of-the-mill except for the subplot about Data trying to learn comedy. He uses the holodeck to create a virtual comedy club, with the real-life comedian Joe Piscopo as the stand-up comic attempting to teach him. Data's attempt at stand-up is another example of Brent Spiner's comic talent: it looks right and yet it is totally, dreadfully, unfunny. (Unfunny as stand-up; funny as Data, though.)
"Shore Leave" (TOS)
A weak rather than bad episode. The crew don't realize that are on a recreation planet which creates things from their thought. Unfortunately they have a lot of rather negative thoughts.
There is a very memorable scene where Kirk meets Ruth, summoned into existence by his wistful thoughts. He is overwhelmed by emotion, even though he thinks it can't be real. The music intensifies the feeling. But who is Ruth? He hasn't seen her for fifteen years. She is probably intended to be an old girlfriend (obviously rather special). But when I first saw it, the intensity of Kirk's response gave me the impression that in fact the real Ruth may be dead. (I'm not the only one to have got this impression.) The way Ruth approaches him, slowly, also contributes to the impression that there is something very strange happening. "You haven't told me—you haven't told me" Kirk says helplessly. Words are insufficient for the questions that were never answered. However you read it, it's outside Kirk's usual affairs.