For me, the worst episode is "The Counter-clock Incident." It's a totally nonsensical episode in every way. If time ran backward in the other universe, wouldn't their minds run backward too so they'd perceive it as forward? Not to mention the way four unrelated forms of inversion were lumped together even though there's no possible causal relation: temporal inversion (aging backward), functional inversion (controls working in reverse), directional inversion (ships flying backward), and
color inversion (black stars on white space). The whole thing is just so stupid. Although baby Arex is cute.
"The Practical Joker" is also a stupid episode. It makes no sense that a malfunction created by flying through a cosmic cloud could be cured by flying through it
again. That's about as credible as the sitcom cure for amnesia, a second bump on the head. (As a kid, I assumed it was because the ship had flown through in the opposite direction the second time. But the episode doesn't specify, so even that juvenile logic can't explain it.) Worse, though, is that the crewmembers are completely out of character. I can't buy that intelligent adults like them would break up laughing over such simpleminded, juvenile pranks. Not that I don't think they might enjoy a good prank, I just don't think the pranks here rose anywhere near the level of
good pranks, at least not in the mind of anyone older than eight. (And the proto-holodeck doesn't salvage it for me, since it's way too advanced for the period, given that holodecks seemed to be a novelty in TNG.)
It was hard to pick a third choice. I'm not fond of "More Tribbles, More Troubles" because the plot doesn't make sense. Why does the transporter work the second time the stasis beam is used when it was frozen the first time? Also, it makes no sense that Kirk would beam the tribbles over
before issuing his ultimatum. Why blow his leverage like that? I'm also not particularly fond of "Mudd's Women" because its portrayal of Chapel is rather degrading.
But I had to go with "The Magicks of Megas-tu." Not that it's a bad story in itself, but I have serious problems with two of its core concepts, in two very different ways. One is its heavy reliance on the continuous-creation model of cosmology, which has been thoroughly disproven and makes the episode as badly dated as a story about jungles on Venus. The other is its conceit that the Salem witch trials were a response to genuine supernatural phenomena. Those trials were a profound atrocity arising from a culture's pathological fear of feminine power and independence and a few individuals' cruelty toward their neighbors. And any story that sweeps that under the rug by claiming there was real magic behind it... well, it's like Holocaust denial on a smaller scale. It's trivializing a historical tragedy we can't allow ourselves to gloss over. Not to mention that in more general terms, the whole "aliens responsible for our folklore and mythology" trope was already a cliche at the time.
Which is a shame, since aside from those things, there's a lot to like about the episode.
(Actually, I kind of like how we tend to raise our children exposed to less violence (and more boobs) here in western Europe compared to the US.)
You guys are so lucky over there...
Finally, while I also like the TERRATIN episode, something strange and unexplained also happens right at the end, involving just how the city gets up to the Enterprise. It seems it's beamed up by way of a PHASER BEAM? Again, makes no sense.
Wasn't that a tractor beam? Or a visual representation of a transporter beam?