I'll pardon such offences as “Spock's Brain” and “Shades of Gray” (ST:TOS3 and ST:TNG2), on the grounds that American TV has a statutory minimum cheese content. Besides, any real “Star Trek Mark Two” (say, a twenty‐first‐century remake for holovision!) can start from scratch, omitting unworthwhile plots. I'll confine my comments to defining some types of plotline to beware of.
One of the perils of ST:TOS's planet‐per‐episode format and its improvised continuity was the temptation to throw in oneshot plot devices, to be discovered one week and forgotten the next. Such dangling plot threads were all very well in the short term; they could be woven by fans into interesting Trekkie novels. But their cumulative effect when magnified by ST:TNG's projection of the timeline is terrible. Whatever happened to:
You may notice that the above omits all the oneshot Star Trek Universe time‐travel techniques; discussing continuity is futile when plots breach causality! But they could attempt to assume a consistent system of Star Trek chronophysics. For example:
Note that traditional time‐paradox dogma can stand little real scrutiny. Why should an autoassassin “vanish”? A can of worms better left unopened.
This is a recurring strategic error in the battle for plausible Star Trek continuity. What happens is that a scriptwriter notices a logical flaw in previous plotlines and pointedly avoids it on this one occasion, in a counterproductive and inconsistent fashion. Memorable examples include:
Such revisions call attention to the stupidity of the rule to which they are the one exception, while preventing the use of simple blanket explanations – e.g. if it weren't for “The Wrath of Khan” (ST:TMP2), I could claim all the apparent two‐dimensionality was just a further viewscreen conventionalisation.
Formularisation is compulsory in commercial TV, and has struck ST:TNG hard. The NCC1701D now has less time than ever to explore strange new worlds – half the season is prebooked for return visits to the Klingons or Cardassians, and guest spots for Barclay, Ma Troi, Q, Old Uncle Tom Cobleigh and all. Not that I want to see any fewer Romulan Warbirds, Borg mother[―]ships etc.; I just regret this inevitable loss of novelty in favour of the kind of petty continuity that ST:TOS tried so hard to avoid.
|Remember that the whole message of “Balance of Terror” (ST:TOS1) was that such “secret weapons” are only a temporary advantage; next time they met, Starfleet would have cloaking technology and the Romulans would have, say, quark bombs.
|There is a useful distinction to be made between the kind of “continuity” that refers backward to previously introduced concepts (often taken to the extreme of fannish in‐jokes) and the kind that refers forward to developments planned for later seasons (e.g. the failed attempt in “Conspiracy”, ST:TNG1). The last and least important kind of “continuity” is the sort of pointless trivia dealt with in the “Nitpicker's Guide” books – give me a “Kneecapper's Guide” any day! [Footnote postscript: no, that wasn't intended as a “Continuity IRA” joke…]
|The bane of round‐robin universe‐design is the phenomenon of Concept Erosion, of which the Borg are a perfect example. As introduced in ST:TNG2, they were a threat which should soon have been consuming all of Starfleet's resources; but each time they turn up, they are diluted further by writers who have clearly failed to grasp the point that the Borg are tougher and smarter than anyone else. Oh, and Uncle Tom Cobleigh is a character in the folk‐ballad “Widecombe Fair” – I've no idea what he's doing in this rant.
|There's no pardoning cheese like Voyager's; and yes, I am thinking specifically of “Learning Curve” (ST:V1)… See also my pages on SF Chronophysics, Xenolinguistics, and Exobiology.
|Babylon 5 has scrupulously avoided continuity busters – even the magic Back‐to‐Life machine wasn't forgotten! Meanwhile Star Trek has juryrigged an excuse for Starfleet's lack of cloaking devices: they signed a treaty (why?!) which gave precise blueprints for the kind of machine they promised never to invent.
|Even as a self‐appointed chronophysics pundit, I found B5's time‐travel superplot very impressive. On the other hand, the Star Trek movies (as well as ST:TNG7's “And Good Riddance” – sorry, “All Good Things”) have been getting stupider and stupider.
|The Star Trek Universe barely aspires to retrograde continuity, let alone anterograde foreshadowing. Big Mysteries are never resolved because the writers never had any plausible solution in mind (X‑Files syndrome: the truth is not there), and everybody's Character Reset buttons get pressed after each episode.
|“First Contact” (ST:TMP8) subjects the Borg to further fan‐fiction‐by‐committee concept erosion. Practically the first two things we learned about the Borg were that they're (a) sexless and (b) decentralised! The only explanation for the “Borg Queen” is that they've heard of “hive‐minds” (and watched “Aliens”) but know sod‐all about real hives.