1. "THE CITY ON THE EDGE OF FOREVER" - So much has been said about this episode that I can only repeat where others have gone before: brilliant; moving; "gold" (as one film school mate of mine said).
"A question. Since before your sun burned hot in space and before your race was born, I have awaited a question."
The Guardian of Forever is one of the most remarkable characters from the entire series, in addition to being a strong and unforgettable image ("the doughnut"). Actress Joan Collins is not reading lines for some tv show, she is Edith Keeler; sweet, noble, and strong. William Shatner, as Captain Kirk, proves he is an outstanding actor. He makes you believe that he has fallen for Keeler, and somehow, with a little help from the various production departments, does it all in much less than fifty-minutes. Kirk's pained expression at the story's end is a Master-Class Moment... he says not one word. (Screenplay students, take note.)
Shatner and Leonard Nimoy, who enjoyed many fine moments as a team throughout the series, have never been better together than they are here. The interplay is that of the kind expected between friends caught in a hole, but the dynamic of Commanding Officer and subordinate is never lost.
Director Joseph Pevney guides everything with an experienced sure hand (it does not hurt that the man started out as an actor). Composer Fred Steiner wrote an affecting score, at key moments weaving his own music with the old penny arcade song "Goodnight Sweetheart".
Special note: Harlan Ellison wrote the original script, and if you are aware of the seismic events of the behind-the-scenes story, you know that the feisty writer was upset that his work was rewritten (by several people). My take on the subject is that Ellison's teleplay was so good that it was almost impossible for someone to screw it up. It's a gem of a story. (Ellison's original script went on to win a Writers Guild of America award, and the filmed show went on to win a Hugo Award and to be regarded as possibly the fairest Trek of them all.)
Punchline: This episode is one of the greatest examples of hour-long dramatic television that I have ever seen. Period.
"Let's get the hell out of here."
2. "BALANCE OF TERROR" - We have a cool-looking and iconic alien spaceship (the Romulan "Bird of Prey"); three-dimensional 'baddies'; Enterprise crew-members we grow to like, and not so much, in a very short time; a great musical riff; affecting and dramatic space action (with spaceships firing at each other from positions thousands of miles apart, the way it should be); an absolutely superb script; and a moving denouement.
It all starts with a wedding....
Basically a retelling of The Enemy Below, a fine and exciting film from 1957 starring Robert Mitchum and Curt Jurgens, "Balance of Terror" throws, seamlessly, a love interest into the greater picture in addition to replacing a destroyer and a U-boat with two mighty starships ("The Praetor's finest and proudest flagship...").
At the risk of over-simplifying an arguable point I will say that only Star Trek could pull off a story like "Balance of Terror". Conjuring up space-battle-action on the script page is easy (and relatively cheap to render visually, today), but to fuse it so impeccably with a people-story that matters seems to be the great unsolvable equation for many a filmmaker; especially these days. Firing phasers and photon torpedoes mean nothing, except to the worst of the geeks, if you don't underlay science fiction-type artillery with a narrative of emotional weight -- otherwise, it just ends up a story of procedures and protocols.
The Romulans manning the great Bird of Prey are not given short shrift here. The anguish of doing the right thing for home and country, and the Praetor, while at the same time wondering what it all really means at the end of the day, injects the 'enemy' scenes with more than the typical shallow stock bad-guy shenanigans. The Romulans have emotions, too; a vital lesson in today's political climate of readily labelling any opponent as "scumbags".
The bookends to this technically and tactically oriented tale are basically that of love and loss. ("Spoiler Alert", all decks!) Captain Kirk has another job responsibility, outside of giving the expected orders necessary in running a ship-of-the-line; one of consoling a bride who lost her loved one in an aimless and unnecessary war ("It never makes any sense. We both have to know that there was a reason.").
I suppose the theme of "Balance of Terror" is loss: machine; pride; integrity; self; and humanity. A story for the ages.
"In a different reality, I could have called you 'friend'."
3. "MIRROR, MIRROR" - As my brother said to me a few years ago with rolling glee, after watching this episode earlier that day, "('Mirror, Mirror') has to be one of the most entertaining pieces of television ever made". Rarely has a television series' regular cast had such an obvious field-day playing, with great aplomb, a step or two outside of the usual sandbox.
Jerome Bixby's script is from teleplay-heaven. It should be studied in screenwriting classes. I'm serious. Every word of dialogue, every scene, every motivation, counts and drives the story forward. There's a plate-full of tasty dialogue ("Indeed, his act warrants death."); the 'other' Spock is delectably dark, but still Spock; there are memorable characters who are essentially just walk-ons ("Yes!, Sir!"; "Smart boy, switching to the top dog."); and as evil as this alternate world is, everyone, bad guys included, has a sense of humour -- even if they don't mean to be funny.
My most personal admission for "Mirror, Mirror" is that it did not resonate for me, really, until my teens. I remember watching it one weekend afternoon when I was seventeen, and suddenly the episode exploded into 3-strip Technicolor. Sure, I loved it as a kid ("Spock with a beard"), of course, but a little life experience was needed to process and fully appreciate all its themes; and to 'see' its delicious humour.
This line, more than any other perhaps, in a script which is loaded to begin with, may illustrate the overall tone of the alternate universe Enterprise perfectly....
"And my Sickbay is a chamber of horrors. My assistants were betting on the tolerance of an injured man. How long it would take him to pass out from the pain."