I chose this particular episode because the premise sounded a lot like "The Thing" which is one of my favorite horror movies. And that's how this episode opens: a lone security guard in a tunnel, threatened by a monster we don't see, and much screaming in grand slasher-movie-style. Fortunately, the episode unfolds differently, and to great Star Trek effect/commentary on the state of humanity. The Enterprise has rushed to help a mining colony planet that digs out pergium (which I kept mis-hearing as per diem, making the episode a lot more ridiculous in very short order) where 50 people have been killed by a mysterious monster in the 3 months since the mine's tools discovered a new vein of rock/minerals and a cavern filled with thousands of round objects that the miners think are "silicon nodules." Even though the outcome of this episode is obvious from the first five minutes, it didn't drag or slow, and that's saying something. Usually, when I watch shows from the 50s/60s, I find the pacing glacial at best. Star Trek didn't have this problem, and that was really refreshing.
Anyway, the Enterprise gets there, our heroes talk to the mine's foreman, deal with one of the hotter-headed miners, who wants to kill the monster ASAP for revenge purposes, and then try to discern what the monster could be. Spock speculates that the monster isn't a carbon-based life form because of the conditions in which it lives, but Bones scoffs. Then the monster steals a vital part from the nuclear reactor that powers the mine, and everyone's thoughts turn to killing it. Fortunately, Kirk is the one who discovers the monster, and he quickly realizes it's not some mindless killing machine. At this point, I really have to give the prop masters and set designers credit because this monster, the Horta, looks like a pile of glowing barf, and convincingly disgusting and alien. It's also nice to see a non-humanoid alien, too, and whatever actor is buried underneath that suit deserves kudos for making this thing a realistic monster. But the most interesting part of the episode is Spock's mindmeld with the creature, which is unbearably sad when taken out of context: "Sadness for the end of things," he whispers. Sadness, indeed. It's then revealed that the silicon nodules were actually the Horta's eggs and the miners had been destroying them (seriously), so the Horta struck back. With Spock's help, the miners and the Horta work out a deal to mine more effectively and not hurt the Horta's eggs, which quickly hatch. Yay for everyone!
There were several things I really liked about this episode, most notably Spock's initial focus on research over conquest. Early on, he says that killing the creature would be "a crime against science," and although he abandons this stance in short order, it plants the seed in Kirk's mind that perhaps the Enterprise crew shouldn't go in with guns (er, phasers) blazing. I also like the episode for the unique creature concept, and the idea that cooperation, rather than destruction, saves the day. It's a very optimistic view of the future, and one that I wish more shows/stories would embrace.
Less optimistic and far more bonkers is "Mirror, Mirror," an episode which asks its viewers to suspend their disbelief that 1) there is a mirror universe in which all of our main characters have EXACT DOUBLES; 2) these EXACT DOUBLES are doing the EXACT SAME THING as our heroes at the EXACT SAME TIME; and 3) a
The alternate universe is EEEVVVIIILLLLLL: assassination is the only way to advance in rank; crew members who make mistakes are tortured; and failed mutinies are met with torture and death. Evil!Spock is rocking a goatee and everyone's uniforms are more ridiculous than ever. The ladies' outfits, in particular, look like NFL cheerleaders' uniforms as designed by Hot Topic. Fortunately, our heroes are able to blend in by being evil-ish and ignoring certain things (although Kirk is pretty appalled at everything he sees, and does some small stuff that helps Evil!Spock figure out what's actually going on.)
Meanwhile, in the home universe, regular Spock figures out pretty quickly that his comrades aren't right and confines them to the brig, with a slightly amused expression that makes me think of a parent catching kids mid-shenanigans.
In the EVIL!universe, our heroes sort out what they have to do to get back, and a semi-ridiculous plan is hatched, wherein Scotty will sneak into Engineering to fiddle with something, Uhura will distract Evil!Sulu so that he doesn't notice... that messing with stuff, and Bones and Kirk will just survive and get the hell out. Of course, nothing is that easy, and Kirk is semi-seduced by an evil!lite!crew lady who we've never seen before, but apparently is evil!Kirk's evil girlfriend. During this seduction (which is accompanied by the flute music of seduction evil), it's revealed that evil!Kirk has a... I dunno, "kill everyone who opposes me" button poorly disguised on his wall. Wow, dude. I wish I had plot devices laid out as obviously around me sometimes! Eventually, though, everyone makes it back to the transporter room, Kirk sows the seeds of rebellion with Evil!Spock, and the universes are realigned. I think.
The best part of this episode, by far, is Uhura. Although she doesn't get nearly enough screen time, and there's a weird scene with her early on, when she is on, she PWNS it. Evil!Sulu tries to seduce her in a creepy way? She shuts it down! A distraction is needed later on? She rocks it! A fight breaks out in sick bay? She fights along with her comrades! Evil!lite!Girlfriend tries to stop them from teleporting out of the evil universe? Uhura stops that, too! I just wanted to watch the episode where she sneaks around the evil Enterprise, planning and blending in, but never compromising her principles. This part was great!
Awesome-est moment in both episodes: I had forgotten the storytelling conceit that Kirk, Spock, and Bones have a little summation on the bridge at the end of both of these episodes, and these scenes were really good. Spock got some funny zingers, and the friendship (or more, whatever you want to see there) was well-expressed and rather touching.
Least awesome-est moment: Too many dicks on the dance floor. Seriously: there is only one woman in "The Devil in the Dark" and she doesn't even get a speaking line; while there are two women in "Mirror, Mirror", only Uhura gets any real agency. I'm glad that Next Gen, for all its contrivances and weird bits rectifies this problem to mostly very good effect.
Most Ridiculous Thing from my notes: "Coffee break! Eyebrow!" & "Semantics~~~~~"