In a way it is reminiscent of the RTD era of Dr Who, with a massive alien threat being at the heart of the finale. It certainly is the best of the three season finales.
Not really. It's a staple sci-fi trope going back decades, long before even Jon Pertwee's era of Doctor Who, Quatermass, and so on.
Trek just used the old "aliens are coming to take over, from the perspective of the Earth people" trope and applied it to an established human colony on some another world, innovating on the trope to a new level -- while sprinkling in an interesting mystery whose answer is hidden in plain sight at the very start but in a clever way. And with stereotyped caricatures of Kirk's family (very 1960s) too, but one can't have everything. I don't recall any RTD era story where we didn't get an alien POV the way "Annihilate" had and not all baddies need to have a big backstory, or even any dialogue. Like how "War of the Worlds" was.
"Operation Annihilate" is certainly TOS's best season finale but in the end is that honestly saying all that much?? How it's produced, the lack of attempted levity, a neat (but a little dated) bit of real science (UV frying the fritters but leaving its human host cancer-free? But that aside, for the time, it's not that
bad), and a simple tale well-told make this more than the sum of its parts. I also recognize what might be - in the location shoots - the IADC building filmed for
Wonder Woman and the courtyard and steps used in
Conquest of the Planet of the Apes. The area does have quite a good look for it.
With "Assignment Earth" being a bit too hokey with its treasure hunt list of items like: Why kidnap humans from 4000BC to train them through the ages - inbreeding was already a known issue in the 1960s and too many documented cases of physical and psychological problems render the concept moot (at best). Why does the Enterprise need to time travel so often for historical research when any attempt to do so could easily alter the timeline significantly (this isn't high concept Doctor Who, this is a one-off episode of Trek that has its own set of rules and ST IV TVH used a proper reason ("if we don't risk this drastic step we're doomed") and not a silly throwaway one like ("Oh, we just went back in time for tea. You like that, right?"). Worse, imagine if the whale movie started with "Well there's this probe sucking energy from everything and there are no whales so we popped back in time because we heard a message and we were at a safe distance so here we are now, let's have fun." Ugh. Aren't we all lucky that Roberta was fiddling with Gary's knobs at just the right time so he wouldn't be captured by the Enterprise? There's also Gary's magic wand near-panacea had me thinking RTD in a few too many scenes to buy into it after a while. What doesn't it do, the laundry and dishes? (That's a $0.02 add-on, no doubt.) Never mind the pomposity of how the 1960s were Earth's most contentious time period (seriously, If the claim was even remotely sincere they'd hire a temporal taxi service to check out decade after decade, all while not scribbling their phone number on the bathroom stall wall), then add in some extremely lame attempts with comedy scenes with accompanying music because it must be a funny scene... amazingly they didn't opt for a laugh track... at least Spock pointed out the planet was loaded with crises, "Current Earth crises would fill a tape bank", when asked by Kirk for a historical report - even though their being there could risk changing history...)
But as finales go, "Assignment Earth" is ultimately on par with "Turnabout Intruder" -- not a good story but for very differing reasons. The latter at least had a new way to use body swapping in an attempt to commandeer the ship all while the crew go on edge over their commander acting increasingly different, but the "Assignment Earth" finale goes in more directions than any of my posts do. It'd actually be worse than "Turnabout Intruder" except that when applying a belief that the episode acts as a "time capsule", it's almost tolerable. The problem with that is that the episode was officially used as a backdoor pilot (thus robbing a standalone TOS episode as a result): Consider the last five minutes or so, forget the preceding forty five minutes of awesome hi-jinx: Kirk and Spock stand around, pretend they know nothing to ramp up phony melodrama, then one scene later - without looking anything up - all grin and say how everything happened precisely as it's supposed to (What, they didn't change anything?
They wouldn't know if they had!) and how Gary and Roberta are in for lots of groovy adventures together... It's an atrociously bad script, and given it wasn't picked up as a series it's not too difficult to guess as to who felt insulted by the script as presented the most.
On the plus side, the computer countdown stopping after 140 and to the point of the bright flash felt very much in continuity (stopping at 104, I was keeping time... that's impressive since Doomsday Machine and others didn't sync up various timer counts with the moment of impending dramatic demise... yet Doomsday Machine, et al, are pretty much all better stories, told better.)
On the minus side, I was also keeping track of various loudspeaker and computer voices and wondering how many might not have been done by Doohan or Babcock (who were genuinely great but after a while, the cadence can become a giveaway. It's a lot easier to figure out who plays who on The Simpsons and in the same way too... the point is, the moment one is drawn out of the story... like wondering how all those glass wine glasses didn't fall off when the wall opened up and being the 1960s when boozing was as common as smoking and yet nobody every tried to pick one up and find out "IT'S A FAAAAAAAAAAAAKE!"... Sorry, had to inject something from "In The Pale Moonlight" of DS9 fame...)
