History InnocuouslyImportantEpisode / LiveActionTV

* The ''Series/MurdochMysteries'' MusicalEpisode is the last place you'd expect a major plot thread to be wrapped up, especially as most of it takes place inside Murdoch's mind, but the killer of the week turens out to be [[spoiler: Ralph Fellowes, resulting in Murdoch both learning that he's still alive ''and'' finally arresting him]].

** The first season episode "Shoot" seems at first glance to be a character study of Betty Draper, exploring her past as a sophisticated model and what she gave up to be Don's wife. However, it introduced or foreshadowed several major elements of the show, including [[spoiler:McCann Erickson's looming presence and desire to acquire Don, the Coca-Cola account, Don's marriage to "European, more Audrey Hepburn style" Megan, and Betty's death from lung cancer]].

** The Season 15 episode "Wednesday's Child" has the squad finding a missing boy who was given away by his stressed out foster mother to an adoption agency who unknowingly gave him to parents who are child pornography producers. The squad arrests the couple and find the children involved. One of those children, however, is an unclaimed baby boy that Olivia adopts and eventually becomes her son Noah.

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** [[Recap/DoctorWhoS4E2TheTenthPlanet "The Tenth Planet"]] has three main points about it that get very important later. It introduced the "Base under Siege" formula that would dominate Troughton's tenure and influence the show's slide from a GenreRoulette format into MonsterOfTheWeek, introduced the Cybermen (though they were given a soft-reboot a few episodes later), and ended with a shock twist of the Doctor suddenly turning into a totally different actor. All of these at the time were just decisions being made for that particular episode and RealLifeWritesThePlot, but due to ''Who'''s KudzuPlot nature all became very significant (although some in terms of the show's feel rather than in plot points).

** [[Recap/DoctorWhoS30E2TheFiresOfPompeii "The Fires of Pompeii"]] initially appears to be a standard MonsterOfTheWeek/Historical Period of the Week episode, but even aside from the standard {{foreshadowing}} and {{Casting Gag}}s, the events of this episode directly influence the Twelfth Doctor's [[Creator/PeterCapaldi choice of appearance]] 6 RealLife years later (about 1200 InUniverse).

** An early Ferengi comedy episode "[[Recap/StarTrekDeepSpaceNineS02E07RulesOfAcquisition Rules of Acquisition]]" shows Quark haplessly navigating a complicated relationship while he pursues business opportunities in the Gamma Quadrant. In the process, he's told that he can't do business there without dealing with a major power known as "The Dominion". The war against the Dominion is ''the'' MythArc of the show.

** ''Series/PowerRangersRPM'''s "Tenaya 7" not only properly introduces the titular cyborg villainess but also before she blows her cover, a throwaway line about a metal detector getting "false positives" gains new meaning when in the two-part finale [[spoiler:BigBad activates the sleeper drones among half of [[DomedHometown Corinth's]] populace including ''the officer'' who says ''said line'']].
** ''Series/MightyMorphinPowerRangers'' season 3's "Master Vile and the Metallic Armor" introduces the Zeo Crystal which not only serves to reverse the time shift in the Alien Rangers arc, but also its later attempted theft causes [[spoiler: the Command Center's bombing]] and later serves as the basis of [[Series/PowerRangersZeo the next season]]'s powers.
** And than ''Zeo'' mentions its BigBad's ties to an "alliance of evil" which is later prophised in the Millennium Message of ''Series/PowerRangersTurbo'', then [[spoiler:abducts mentor Zordon]] and plays a big role in the Zordon Era's GrandFinale ''Series/PowerRangersInSpace''.

* ''Series/{{NCIS}}'': "One Man's Trash" was a general episode involving a cold case and antique dealers. The episode also introduces the audience to Kasie Hines, [[spoiler: the next forensic scientist of Team Gibbs and Abby Sciuto's sucessor]], who is initially presented in the manner one would expect to see out of a one-shot or as a recurring character in this series.

** "[[Recap/BuffyTheVampireSlayerS3E10Amends Amends]]" was just a liked but cheesy little ChristmasEpisode from Season 3... but you'll need to remember it to understand the machinations of the BigBad come Season 7.

** The thirteenth episode "[[{{Recap/BabylonFiveS01E13SignsAndPortents}} Signs and Portents]]". The episode's "A" plot is some fairly standard and unimportant thing involving Raiders [space pirates] and a Centauri artifact called The Eye. The "B" plot, involving the first appearance of the enigmatic Mr Morden and the question "What do you want?", turns out to be ''incredibly'' important and crucial to the rest of the series -- but the episode's retrospective importance only kicks in at the first season finale.\\
*** Its importance was lampshaded by the fact that the entire first season was also named "Signs and Portents" (though a casual viewer wouldn't know this - the season titles only appeared on fan sites.) "Portents", of course, are ''[[{{Foreshadowing}} hints about future events.]]''\\

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Its importance was lampshaded by the fact that the entire first season was also named "Signs and Portents" (though a casual viewer wouldn't know this - the season titles only appeared on fan sites.) "Portents", of course, are ''[[{{Foreshadowing}} hints about future events.]]''\\
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The A Plot does have one rather important thing happen in it: it's the first appearance of [[BigBad The Shadows]]. They even get name dropped, but in a way that most viewers would dismiss as unimportant on a first viewing.

** The second episode of the second season, ''Revelations'' features a bunch of important plot bits about G'Kar, Garibaldi and Delenn in particular - and also a B-plot featuring Sheridan coming to terms with the death of his wife Anna after getting a last message from her (brought to him by his sister). At the time, it seems like little more than a bit of character development for the new guy, but Anna Sheridan will turn out to be incredibly important to one episode later in this season, and even more important the last few episodes of the next.

** And speaking of Ro, her debut episode "Ensign Ro" also introduced the Bajorans, who would take center stage on ''Deep Space Nine''.

** "[[Recap/StarTrekTheNextGenerationS4E12TheWounded The Wounded]]". By itself it seems like another diplomatic problem-solving episode. But it is a DayInTheLimelight episode for recurring character Miles O'Brien which sees the introduction of the Cardassians, as well as inserting a {{Retcon}} changing the previously-asserted general peace in which the Federation was said to have existed for decades and replacing it with a GreatOffscreenWar. This would serve as the starting point for O'Brien's promotion to main character on ''Series/StarTrekDeepSpaceNine'', as well as the emergence of the Maquis and the Dominion War over on [=DS9=] -- which in turn serves as the catalyst for ''Series/StarTrekVoyager''. Also, Wesley Crusher's departure in "Journey's End" and the defection of Ro Laren during TNG's penultimate episode stem from this episode.

** "[[Recap/StarTrekTheNextGenerationS4E12TheWounded The Wounded]]". By itself it seems like another diplomatic problem-solving episode. But it is the introduction of the Cardassians, as well as inserting a {{Retcon}} changing the previously-asserted general peace in which the Federation was said to have existed for decades and replacing it with a GreatOffscreenWar. This would serve as the starting point for the emergence of the Maquis and the Dominion War over on ''Series/StarTrekDeepSpaceNine'' -- which in turn serves as the catalyst for ''Series/StarTrekVoyager''. Also, Wesley Crusher's departure in "Journey's End" and the defection of Ro Laren during TNG's penultimate episode stem from this episode.

* ''Series/{{Gotham}}''[='=]s episode "[[Recap/GothamS1E16TheBlindFortuneTeller The Blind Fortune Teller]]" appears simply to be an episode set at a circus featuring ''[[Series/ShamelessUS Shameless]]''[='=]s Creator/CameronMonaghan. Whose character then displays both a SlasherSmile and EvilLaugh, behavior very [[ComicBook/TheJoker familiar]] to ''Franchise/{{Batman}}'' fans. [[spoiler: He doesn't actually turn out to be the Joker, but he plays a key rolein corrupting the true Joker...who also happens to be his identical twin brother.]]

** [[Recap/DoctorWhoS1E2TheDaleks "The Daleks"]] was initially written as a space adventure story based on 1950s sci-fi serials, with anti-war themes and some [[TheGrotesque quirky]] [[ANaziByAnyOtherName Nazi-like]] "bug-eyed monsters" as villains. Due to the extreme popularity of aforementioned villains, it is now impossible to watch the story without being aware that this is the Doctor's first encounter with the Daleks.

** "[[Recap/BreakingBadS2E7NegroYAzul Negro y Azul]]" has the A-plot being Walt and Jesse dealing with the fallout of Spooge's death at the hands of his wife, but this episode introduces Beneke Fabricators as well as the Cartel, [[spoiler:the former's boss Ted Beneke having an affair with Skyler post her knowing that Walt's a meth cook, causing huge troubles in Season 3, as well as Beneke's cooking the books and Skyler's attempts to cover it becoming the major factors in the resolution of Season 4, as well as the Cousins (who killed Tortuga) becoming major antagonists in the next season, and their deaths leading to Gus Fring slowly taking over the Cartel, which, again is one of the factors for the second half of Season 4.]]

** [[Recap/DoctorWhoS13E5TheBrainOfMorbius "The Brain of Morbius"]] was intended as a {{Filler}} BottleEpisode, but several of the Doctor's throwaway lines in the story imply that the Time Lords aren't as godlike and advanced as they had previously been portrayed. This could easily be brushed off by the fact that the Doctor hates the Time Lords and (in that incarnation at least) [[{{Cloudcuckoolander}} has an unreliable grasp on reality]], but Robert Holmes picked up on it and used it as {{Foreshadowing}} for his WhamEpisode, [[Recap/DoctorWhoS14E3TheDeadlyAssassin "The Deadly Assassin"]], which revealed the Time Lords were a bunch of stagnant old politicians with ChronicBackstabbingDisorder.
*** And then, more than 30 years later, "The Brain of Morbius" would become ''even more'' important: during the mindbending contest, we see flashbacks to all of the Doctor's past incarnations... along with eight other men, whose identity is not commented on but who were intended at the time to be incarnations of the Doctor prior to the first. [[spoiler:[[Recap/DoctorWhoS38E10TheTimelessChildren "The Timeless Children"]] reveals that ''that is absolutely the case'', and that the Doctor has had countless lives that even they were unaware of until the end of Series 12.]]
---->'''Morbius:''' [[{{Foreshadowing}} How far back, Doctor? How long have you lived?]]

** "[[Recap/StarTrekTheNextGenerationS2E17SamaritanSnare Samaritan Snare]]" introduces the Pakleds, a species of idiots whose only edge is being just smart enough to perform a WoundedGazelleGambit in order to steal technology. The Pakleds return in the first-season finale of ''WesternAnimation/StarTrekLowerDecks'', having grown strong enough to steal Federation technology by force, and harass the Federation continually for the entire second season.