* ArchivePanic: 49 episodes, each running around 50 minutes. It takes 30 hours and 50 minutes, or well over a full day, to watch the entire B&W series.
* BizarroEpisode: "Controlled Experiment" is an oddball of the original series due to its unusual comedic tone.
* CrowningMusicOfAwesome:
** The series' first season had impressive orchestrated scores, especially for episodes like "The Galaxy Being" (which created music cues frequently used throughout the series), the transformation sequence in "The Sixth Finger", and whenever the telepathic power manifests in "The Man With The Power".
** The positively eerie opening theme of Season 1, which became a recurring {{Leitmotif}} through its episodes. The second season ditched the lavish orchestrated scores for more standard sci-fi fare, but the second opening jingle is still pretty memorable.
** And the heart-wrenching, inspiring music that plays in the last scene of "A Feasibility Study" [[spoiler: as everyone in town joins hands to perform a HeroicSacrifice.]] It got reused in a couple of other episodes, too.
* EnsembleDarkhorse: The original design for the Ghost of Private Gordon in "Human Factor", nicknamed "Chill Charlie", never appeared in the series proper, but is a surprisingly popular bear of the series, much more than the episode's actual ghost, due to its very, very creepy design. The Outer Limits trading card series even gave Chill Charlie its own distinctive card from Pvt. Gordon's Ghost, and It even got its own [[http://dimensionaldesigns.com/chillcharlie.html model kit]] released for it!
* FirstInstallmentWins: The revival may have lasted much longer, but the original series seems to be the one most people remember.
* HilariousInHindsight: "Production and Decay of Strange Particles" has a character played by Creator/LeonardNimoy getting killed by radiation--18 years before ''Film/StarTrekIITheWrathOfKhan''.
* NarmCharm: Some episodes run on this, most famously "The Zanti Misfits", where the antagonists are oversized alien ''ants'', but the actors play the terror of the scenes so perfectly straight in spite of that, that it made the episode a CultClassic of sorts.
* NightmareRetardant: The Zanti Misfits from the eponymous episode, not merely for the uneven effects but the sheer fact that they're oversized ants with faces making gurgling sounds.
** The Venusian from "Cold Hands, Warm Heart". It's an obvious ragdoll puppet floating in a water tank.
** The eponymous creature of "Behold, Eck!".
* OneSceneWonder: Creator/LeonardNimoy in "Production and Decay of Strange Particles".
* SeasonalRot: The second season, while not horrible, was of very uneven quality, due in part to it being moved to a Saturday Night Timeslot against ''The Jackie Gleason Show'', which in turn caused major staffers to leave in protest, and then the production budget was cut even lower than it already was, and they tried to make the show more commercial than before. That the second season was a ratings flop and triggered its cancellation midway shows how well that turned out.
* SpecialEffectsFailure: It varies a lot. The title character of "The Galaxy Being" still looks fantastic decades later, as do many of the show's effects (Mr. Zeno's teleportation effect in "The Special One," the energy monster in "It Crawled Out of the Woodwork," and many others). But it's heartbreaking when some of the best scripts gets saddled with some of the worst effects of the series: it can be hard for a modern viewer to watch the classic "Demon With a Glass Hand" because the aliens' makeup jobs and costumes just look so pathetically cheap.
** "The Zanti Misfits" for the most part has excellent stop motion effects for the aliens, but some shots of them, most notably when they're clinging to a person or "crawling" down a wall, are obvious static puppets on strings.
** "The Man With The Power" has the scene where a rock is lifted into the air by the man's mind, where at several points you can clearly see the strings holding it up.
** The alien's makeup from "The Children of Spider County" looks fine until the character is required to talk, at which point you're reminded that it's just an immobile rubber mask.
* TearJerker: The ending of "The Man Who Was Never Born"; Andros succeeds in averting the BadFuture, but at the expense of his own existence, leaving a despairing Noelle alone with the ship hanging in limbo as the screen fades to black...
** The ending of "The Architects of Fear", when Yvette realizes the monster dying in front of her is Allen, whose life was pointlessly sacrificed as the result of a botched GenghisGambit.
** The ending of "A Feasibility Study", [[spoiler: where the entire town performs a HeroicSacrifice together.]]
* TooGoodToLast
* VisualEffectsOfAwesome: The show often achieved impressive effects for a TV show of the time, most famously the Galaxy Being from the eponymous episode.
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