History InnocuouslyImportantEpisode / LiveActionTV

** Although [[ProductionForeshadowing made to promote]] ''Film/StarTrekVITheUndiscoveredCountry'', the [[Recap/StarTrekTheNextGenerationS5E7Unification1 two-part]] [[Recap/StarTrekTheNextGenerationS5E8Unification2 episode]] "Unification" also provides Spock Prime's backstory in [[Film/StarTrek2009 the reboot films]], as we see that Spock was still living on Romulus as an ambassador between the Vulcan and Romulan peoples before Romulus was destroyed by a supernova. Nero, the Romulan BigBad of the 2009 film, is led to think that Spock Prime betrayed his world, and his RoaringRampageOfRevenge [[NothingIsTheSameAnymore radically alters history in the 23rd century]]. This, in turn, also provides the backstory of Captain Picard on ''Series/StarTrekPicard''.

** "[[Recap/BuffyTheVampireSlayerS5E15IWasMadetoLoveYou I Was Made to Love You]]" (and earlier, "[[Recap/BuffyTheVampireSlayerS2E11Ted Ted]]") seemed a bit out of place at the time of airing (robots? really?) but set up the suspension of disbelief needed for the Buffybot to exist in that series, which allowed Dawn to stay in Sunnydale after the events of "[[Recap/BuffyTheVampireSlayerS5E22TheGift The Gift]]". Also, this episode introduced Warren, who would become a major villain in the following season.

* ''Series/{{Gotham}}'''s episode "[[GothamS1E16TheBlindFortuneTeller The Blind Fortune Teller]]" appears simply to be an episode set at a circus featuring ''[[Series/ShamelessUS Shameless]]'''s Creator/CameronMonaghan. Who's character then displays both a SlasherSmile and EvilLaugh, behavior very [[ComicBook/TheJoker familiar]] to ''Franchise/{{Batman}}'' fans.

** "[[Recap/StarTrekTheNextGenerationS1E25TheNeutralZone The Neutral Zone]]" has two plots: the A plot is a fish-out-of-water story about twentiety-century earth humans running amok on the Enterprise; occasionally we touch on how outposts along the Romulan Neutral Zone have been disappearing. This secondary plot is the first time in the franchise that the Borg's influence was hinted at, and similar disappearances would be discussed in their first appearance ("[[Recap/StarTrekTheNextGenerationS2E16QWho Q Who]]") and the landmark Borg two-parter "[[Recap/StarTrekTheNextGenerationS3E26S4E1TheBestOfBothWorlds The Best of Both Worlds]]".

** [[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 choice of appearance 6 RealLife years later (about 1200 InUniverse).

* The ''Series/MadMen'' third season episode "My Old Kentucky Home." On its face, the FourLinesAllWaiting story serves as a series of character vignettes bound by the "work disguised as fun" theme. However, this episode introduces us characters that become prominent in later episodes (Connie Hilton, Henry Francis); and story arcs that carry through the next couple of seasons (Peggy's introduction to the counterculture, Joan realizing that marrying her doctor is not going to give her the life she thought she wanted, Betty looking for a way out of her marriage, among others).

** [[Recap/DoctorWhoS37E2TheGhostMonument "The Ghost Monument"]], the second episode of StoryArc-less Series 11, is a relatively average story about the Doctor and her companions retrieving the TARDIS after it had been separated from the Doctor earlier. Come Series 12, however, it turns out to contain the first reference to [[spoiler:the "Timeless Child", which is connected to the Series 12 arc, part of a lie embedded into Time Lord history that is so terrible it drove the Master even ''crazier'' than he already was and led him to raze Gallifrey.]]

** "[[Recap/StarTrekTheNextGenerationS02E09TheMeasureOfAMan The Measure of a Man]]" was a one off courtroom episode that focused on whether or not Data is sentient life. Turns out the philosophical implications of this episode was so far reaching that it became the primary plot of the entire first season of ''Series/StarTrekPicard''. Losing this case caused Bruce Maddox to create more androids similar to Data. An attempt on the life of one of these androids kicks off the plot of the Picard spinoff.

** Although [[ProductionForeshadowing made to promote]] ''Film/StarTrekVITheUndiscoveredCountry'', the two-part episode "Unification" also provides Spock Prime's backstory in [[Film/StarTrek2009 the reboot films]], as we see that Spock was still living on Romulus as an ambassador between the Vulcan and Romulan peoples before Romulus was destroyed by a supernova. Nero, the Romulan BigBad of the 2009 film, is led to think that Spock Prime betrayed his world, and his RoaringRampageOfRevenge [[NothingIsTheSameAnymore radically alters history in the 23rd century]]. This, in turn, also provides the backstory of Captain Picard on ''Series/StarTrekPicard''.

** [[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?]]

* ''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/BuffyTheVampireSlayerS5E15IWasMadetoLoveYou}} I Was Made to Love You]]" (and earlier, "[[{{Recap/BuffyTheVampireSlayerS2E11Ted}} Ted]]") seemed a bit out of place at the time of airing (robots? really?) but set up the suspension of disbelief needed for the Buffybot to exist in that series, which allowed Dawn to stay in Sunnydale after the events of "[[{{Recap/BuffyTheVampireSlayerS5E22TheGift}} The Gift]]". Also, this episode introduced Warren, who would become a major villain in the following season.
** "[[{{Recap/BuffyTheVampireSlayerS2E18KilledByDeath}} Killed By Death]]". Buffy is sick and ends up in hospital - a place she hates since her cousin died in a hospital when they were children. While the MonsterOfTheWeek in the episode (which was also responsible for her cousin's death) is dealt with, Sunnydale General ends up playing a ''big'' role in Season Five - not only does Buffy's mother Joyce end up with a brain tumor and spends a few episodes there, but we're also, at the same time, introduced to the character Ben Wilkinson, a young medical intern who serves as a possible {{Love Interest|s}} to Buffy [[spoiler: and who turns out to be the mortal, human shell of Glory, the BigBad of Season Five - Glory's plans, in turn, result in Buffy's death in the Season Five finale]].
** In "[[{{Recap/BuffyTheVampireSlayerS4E9Something Blue}} Something Blue]]", Willow loses herself in magic as a way of dealing with Oz's absence and hijinks ensue, one example being Buffy and Spike making out passionately in what is viewed as an in-universe CrackPairing. Things appear to be neatly resolved at the end of the episode, but both Willow's strong emotional reaction to the loss of a significant other (resulting in a misuse of her magical abilities) and the Buffy/Spike romantic chemistry are things that will pop up again in Season 5 and become prominent features of Season 6.

* ''{{Series/Community}}'' foreshadowed Chang's rise to power at Greendale in several earlier season 3 episodes, including [[Recap/CommunityS3E12ContemporaryImpressionists "Contemporary Impressionists"]].

** [[Recap/DoctorWhoS5E5TheWebOfFear "The Web of Fear"]]. Intended at the time as a sequel to an earlier story about the Doctor teaming up with the military and a now-older ally to fight killer robot Yeti in the London Underground. The impact is massive — here is where the Brigadier gets introduced (in fact, he's [[RedHerringMole the prime suspect for being the Great Intelligence's vessel for most of the episode]], something that would not have been done had they known he would be a regular), here is the start of the UNIT arc and here is the start of the "Yeti on the loo in Tooting Bec"-style horror that would form the Pertwee era of the show.

** "[[{{Recap/FarscapeS01E18ABugsLife}} A Bug's Life]]" has a story about Peacekeepers and a virus capable of possessing people, but the repercussions of that episode would echo throughout the series and beyond.
** "[[{{Recap/FarscapeS02E14BewareOfDog}} Beware of Dog]]" had a fairly ridiculous main plot, with a B plot of Crichton going crazy and imagining Scorpius around every corner -- but it's a brilliant setup of the entire plotline for the rest of the season, one that would continue throughout much of the series.
** The very first time Crichton hallucinated Scorpius was in "[[{{Recap/FarscapeS02E04CrackersDontMatter}} Crackers Don't Matter]]", a nutty, off-the-wall episode where everyone's going crazy and fighting over crackers.
** "[[{{Recap/FarscapeS01E16AHumanReaction}} A Human Reaction]]", a well done though not especially memorable episode - until it's revealed a few episodes later that ''the'' major plot point of the ''entire series'' was set up during its events.
** "[[{{Recap/FarscapeS02E15WontGetFooledAgain}} Won't Get Fooled Again]]" seems like just another one of the series' frequent [[BizarroEpisode visits to Bizarroworld]], but the ending reveals the existence of [[spoiler:the neural chip in Crichton's head]] and its accompanying [[spoiler:mental clone of Scorpius]], both of which are crucial to the MythArc.
** "[[{{Recap/FarscapeS03E06EatMe}} Eat Me]]" is just another MonsterOfTheWeek episode, and just another episode where Crichton gets split into duplicates (yes, it happened more than once). Then at the end it turns out that the duplication of Crichton was ''permanent''. Cue most of the rest of the season being split between two groups of characters on separate ships, each with its own Crichton.
* Series/{{Fringe}}'s BizarroEpisode, "Brown Betty" (2x19) at first appears to be funny BreatherEpisode after some important revelations in the previous four episodes. Walter tells Olivia's niece Ella a drug-addled [[MusicalEpisode musical]] [[NoirEpisode noir-style]] detective story using all the regular cast members... then gives the story an incredibly dark and bitter ending about how only one man can have a mechanical heart and one must die without it. The ending reflects Walter's guilt about [[spoiler: stealing Peter and irrevocably damaging the alternate universe]] and how he feels the only good he's ever accomplished has come at the price of destroying children's lives (i.e., the cortexiphan trials). It reflects the major theme of the next season, that only one universe can survive; one must be destroyed, leading to the BadFuture glimpsed in the Season 3 finale, "The Day We Died". However, [[CheerfulChild Ella]] rejects Walter's unhappy ending and creates an ending where the heart can be shared, symbolizing [[spoiler: Peter realizing after seeing the BadFuture there is [[TakeAThirdOption another option]]: he can bridge the two universes, which will heal them both.]] Peter even does this with the aid of a grown-up version of Ella Dunham, bringing it full circle back to "Brown Betty".

** "[[{{Recap/StarTrekS1E14BalanceOfTerror}} Balance of Terror]]" and "[[{{Recap/StarTrekS1E26ErrandOfMercy}} Errand of Mercy]]" introduce the Romulans and Klingons, each of whom goes from VillainOfTheWeek to major galactic power throughout the rest of the franchise.

** "[[{{Recap/StarTrekTheNextGenerationS1E1411001001}} 11001001]]" and, to a greater degree, "[[{{Recap/StarTrekTheNextGenerationS2E3ElementaryDearData}} Elementary, Dear Data]]", introduce the idea of self-aware holographic programs with Minuet and [[Literature/SherlockHolmes Professor Moriarty]], respectively, which would pave the way for other such characters like the Doctor on ''Series/StarTrekVoyager'' and Vic Fontaine on ''Series/StarTrekDeepSpaceNine''.
** "[[{{Recap/StarTrekTheNextGenerationS1E25TheNeutralZone}} The Neutral Zone]]" has two plots: the A plot is a fish-out-of-water story about twentiety-century earth humans running amok on the Enterprise; occasionally we touch on how outposts along the Romulan Neutral Zone have been disappearing. This secondary plot is the first time in the franchise that the Borg's influence was hinted at, and similar disappearances would be discussed in their first appearance ("[[{{Recap/StarTrekTheNextGenerationS2E16QWho}} Q Who]]") and the landmark Borg two-parter "[[{{Recap/StarTrekTheNextGenerationS3E26S4E1TheBestOfBothWorlds}} The Best of Both Worlds]]".
** "[[{{Recap/StarTrekTheNextGenerationS3E17SinsOfTheFather}} Sins of the Father]]" is the first Trek episode to actually feature Klingon society, as Worf tries to clear his deceased father's name when he is blamed for helping the Romulans attack Khitomer, despite dying from the attacks. The episode shows that [[InherentInTheSystem the 24th century Klingon government is extremely corrupt]], as it's discovered that Duras' father was the real traitor, [[DeceasedFallGuyGambit but the Klingon High Council goes along with it to prevent a civil war]], which will have repercussions lasting all the way through ''Series/StarTrekDeepSpaceNine'', [[BookEnds getting rectified by Worf, fittingly enough]].
** "[[{{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.

** 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.
** Season 5's "[[{{Recap/StarTrekDeepSpaceNineS05E10Rapture}} Rapture]]" was a heavy Bajor episode, focusing on the planet's future and Sisko's role as Emissary. The main thrust of the plot is Sisko gaining visions of the future, which are slowly killing him. Before Bashir operates to remove this ability, one vision was of locusts hovering over Bajor before moving onto Cardassia. A later two-parter saw the Dominion enter the Alpha Quadrant and set up shop in its newest member, Cardassia. [[spoiler:The same two-parter also revealed that Bashir had been replaced by a Changeling by this time, offering a new reasoning for "Bashir" wanting to operate on Sisko]].
** Also from Season 5, "[[{{Recap/StarTrekDeepSpaceNineS05E05TheAssignment}} The Assignment]]" is pretty much a standard "O'Brien Must Suffer" episode, as a malevolent alien called a Pah Wraith possesses his wife Keiko and threatens to kill her and their daughter Molly unless O'Brien agrees to sabotage the station. The Pah Wraiths would become major villains in ''Deep Space Nine's'' final season.

* The ''Series/{{NUMB3RS}}'' episode "The Mole" is a story about Colby finding out that [[spoiler:his old Army buddy is a traitor]] and having to choose between friendship and honor, and it appears to be pretty well wrapped up by the end of the episode. The events of the episode end up forming the basis for the season finale and subsequent season premiere, where we learn that that case was just the tip of the iceberg. Not only that, but [[spoiler:Colby has known all along that his friend is a spy, because his friend tried to recruit him too, and Colby's been playing FakeDefector ever since in an attempt to figure out who else is involved.]]

* The ''Series/{{NUMB3RS}}'' episode "The Mole" is a story about Colby finding out that [[spoiler:his old Army buddy is a traitor]] and having to choose between friendship and honor, and it appears to be pretty well wrapped up by the end of the episode. The events of the episode end up forming the basis for the season finale and subsequent season premiere, where we learn that that case was just the tip of the iceberg, and that [[spoiler:Colby's role in the situation is more than it initially appears to be]].

** In series 3 of the new series, [[Recap/DoctorWhoS29E6TheLazarusExperiment "The Lazarus Experiment"]] set up both [[spoiler:Martha's family's betrayal to Harold Saxon/The Master]], and [[spoiler:the aging device was used against the Doctor in the season finale]].
** Similarly, [[Recap/DoctorWhoS29E8HumanNature "Human Nature"]] and [[Recap/DoctorWhoS29E9TheFamilyOfBlood "The Family of Blood"]] appeared to be an updated retelling of [[Recap/DoctorWhoNewAdventuresHumanNature a tie-in novel]], leading to a unique circumstance where fans familiar with the spinoff media were actually less likely to realize these episodes were this trope, which comes off as exceptional filler otherwise. [[spoiler:In fact, they set up the Master's return.]]

** An early random Ferengi comedy episode "[[{{Recap/StarTrekDeepSpaceNineS02E07RulesOfAcquisition}} Rules of Acquisition]]" reveals that something called "the Dominion" is a major power in the Gamma Quadrant. The war against the Dominion is ''the'' MythArc of the show.

** Although [[ProductionForeshadowing made to promote]] ''Film/StarTrekVITheUndiscoveredCountry'', the two-part episode "Unification" also provides Spock Prime's backstory in [[Film/StarTrek2009 the reboot films]], as we see that Spock was still living on Romulus as an ambassador between the Vulcan and Romulan peoples before Romulus was destroyed by a supernova. Nero, the Romulan BigBad of the 2009 film, is led to think that Spock Prime betrayed his world, and his RoaringRampageOfRevenge [[NothingIsTheSameAnymore radically alters history in the 23rd century]].

* The ''Series/{{Charmed}}'' season 2 episode "[=P3H20=]" has the trio meet their mother's old Whitelighter Sam Wilder, who helps them deal with the water demon who killed their mother at the cost of his own life. During the episode, Sam mentions that he and their mother were in love with each other, [[GenerationXerox paralleling Piper's own relationship with Leo]]. This allowed the show to bring in Paige Matthews as the result of the affair and a replacement for the Charmed Ones sisterhood following Prue's death in the season 4 premiere.