History InnocuouslyImportantEpisode / LiveActionTV

** "[[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]].

* ''Series/StargateAtlantis'': In the first season, they encounter a planet that had been developing a drug that would make them immune to the Wraith feeding on them, but also has a 50% chance of killing the person injected. It seems like a one-off story, until the middle of season 4 when their enemy, a Wraith-turned-human-turned-hybrid gets hold of the drug and begins to spread it across the galaxy. It plays an important role in several episodes from then to the end of the series.

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

** "[[Recap/StarTrekTheNextGenerationS2E9TheMeasureOfAMan 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 implication 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.

** ''Series/PowerRangersOperationOverdrive'''s "One Fine Day" was a lighthearted episode featuring the Rangers on a camping trip which gets interrupted when their enemies erect a forcefield to search for part of the season's MacGuffin. A alien-powered human chain used as an attempt to pass through the forcefield is a major clue that [[spoiler:that the Red Ranger isn't human]] when it breaks, foreshadowing his [[spoiler:RoboticReveal]] character arc a few episodes later and his [[spoiler:[[DeathSeeker death-seeking]] HeroicSacrifice]] in the finale.

** ''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 [[spoiler:[[Series/PowerRangersZeo 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 the Zordon Era's GrandFinale ''Series/PowerRangersInSpace''.

* ''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.

** "[[Recap/BreakingBadS1E5GreyMatter Grey Matter]]" has a meeting with Walt's close friends from college, Elliot and Gretchen Schwartz who try to offer him a job, which Walt refuses due to his pride. This will be ''extremely'' important later, as [[spoiler:Walt's ''true'' reason for continuing to cook meth is related to the said friends, as well as both Elliot and Gretchen becoming the only ways Walt can safely handover rest of his money to his family.]]

* ''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. Whose character then displays both a SlasherSmile and EvilLaugh, behavior very [[ComicBook/TheJoker familiar]] to ''Franchise/{{Batman}}'' fans.

* ''Series/TheMandalorian'' has "Chapter 6: The Prisoner" which, by the end of Season 1, was the only episode to not have any connection to the show's continuity. However, once Season 2 came around, a major character from "The Prisoner" reappeared to help rescue Grogu near the end of the season, gaining this own character arc and being the first human in the show to see the titular Mandalorian take off his helmet.

* Two episodes from the first season of ''Series/{{Angel}}'' feature flashbacks that delve into Angel's backstory, paralleling the episodes' events in the present. The flashbacks from ''[[Recap/AngelS01E15TheProdigal The Prodigal]]'' focus on Liam's bad relationship with his father before and after he was sired, in an episode that gave focus to Kate Lockley's relationship with her own father. Those from ''[[Recap/AngelS01E18FiveByFive Five by Five]]'' recount Angel's whereabouts slightly before and after getting cursed with a soul, mirroring Faith Lehane's quest for redemption which starts at the episode's end. But also, the flashbacks introduce (or reintroduce) the audience to Darla, a probably long-forgotten character from ''[[Series/BuffyTheVampireSlayer the parent show]]'', slain [[Recap/BuffyTheVampireSlayerS1E7Angel a few episodes in]], who is then resurrected in the [[Recap/AngelS01E22ToShanshuInLA season finale]] and becomes very important to the show.

** The ending of [[Recap/DoctorWhoS29E2TheShakespeareCode "The Shakespeare Code"]] includes Creator/WilliamShakespeare using words from ''Franchise/HarryPotter'' to stop the villains. The last episode in the season, [[Recap/DoctorWhoS29E13LastOfTheTimeLords "Last of the Time Lords"]], took that concept and turned it UpToEleven. The relationship between the Tenth Doctor and Elizabeth I is later explored in the [[Recap/DoctorWho50thASTheDayOfTheDoctor 50th anniversary special]].

** The Kettleman subplot in season 1 may have seemed like filler at first to establish the kinds of clients Jimmy takes on. But it has major payoff in season 5, as Nacho's dealings with Jimmy during that period lead Lalo to hire Jimmy to be his attorney, which ends up dragging him into the conflict between Lalo and Gus.

** "[[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.

** Season 6's "[[{{Recap/LostS06E12EverybodyLovesHugo}} Everybody Loves Hugo]". Although at first glance the episode is mostly setting up the pieces for the more dramatic twists to come, it features the SurprisinglySuddenDeath of Ilana, many hints to the true nature of the Flash-sideways, and demonstrates Hurley's growing leadership qualities [[spoiler:that ultimately lead him to become the Island's protector at the end of the series.]] It also features Jack vocalizing the realization that he can't take charge of every situation anymore, instead putting his faith in Hurley's judgment, which [[spoiler: is repeated in the GrandFinale when he passes off his role of Island protector to Hurley, claiming that he's the best person for the job.]]

* ''Series/WandaVision'' starts as a lighthearted, if bizarre, installment, but ultimately ends up having important ramifications for phase IV of the MCU: [[spoiler:Wanda becomes the Scarlet Witch and takes Agatha's copy of the Darkhold, setting her up to be co-lead in ''Doctor Strange in the Multiverse of Madness''. The Vision may have returned as the rebuilt White Vision when his memories are restored. Monica Rambeau gains superpowers as a result of traveling through the Hex barrier, and is invited by a Skrull to go into space, setting her up for her role in ''The Marvels'']].

** [[Recap/BetterCallSaulS4E8Coushatta Coushatta]]" seems like a {{Filler}} or BreatherEpisode, but it's actually important to the series since it reveals what all of Gus Fring's plans for Nacho have been building up to and it reveals Lalo showing up to take control of the gang, plus notably, Kim Wexler's FaceHeelTurn (on a sliding scale of evil, not ''that'' evil ''yet'', but still, a grifter).

** [[Recap/DoctorWho2005CSTheChristmasInvasion "The Christmas Invasion"]] appears to be nothing but a ChristmasEpisode to [[EstablishingCharacterMoment establish]] the newly regenerated Tenth Doctor, but it actually set up many events for the next seasons. There's the first appearance of the [[Recap/DoctorWhoS28E12ArmyOfGhosts Torchwood Institute]], the Santa robots come back during [[Recap/DoctorWho2006CSTheRunawayBride Donna's first appearance]], the Doctor [[NiceJobBreakingItHero deposing Harriet Jones, Prime Minister]][[note]]Yes, we know who she is[[/note]] ultimately results in [[Recap/DoctorWhoS29E12TheSoundOfDrums Harold Saxon taking her place]] and last but not least, the Doctor's severed hand is later retrieved by Jack Harkness and become important to both this series and the spinoff ''Series/{{Torchwood}}''.
** The ending of [[Recap/DoctorWhoS29E2TheShakespeareCode "The Shakespeare Code"]] includes Creator/WilliamShakespeare using words to stop the villains. The last episode in the season, [[Recap/DoctorWhoS29E13LastOfTheTimeLords "Last of the Time Lords"]], took that concept and turned it UpToEleven. The relationship between the Tenth Doctor and Elizabeth I is later explored in the [[Recap/DoctorWho50thASTheDayOfTheDoctor 50th anniversary special]].

* ''Series/{{Monk}}'' has its first ChristmasEpisode, which is a standard case of the week with a scene that reveals that Monk is still keeping the last gift his late wife left him wrapped up. It's set up as yet another moment showcasing Monk's undying love for her. Four years later however the GrandFinale reveals [[spoiler:the gift contains all the evidence to find her murderer.]]

* ''Series/{{Frasier}}'': "Back Talk" seems like just another "comedy of misunderstandings" episode in a show full of them, where Daphne mistakenly believes Frasier has fallen in love with her. However, due to being delirious from the painkillers he's taken, Frasier tells Daphne about Niles' secret feelings for her while she's giving him a massage. The studio audience actually gasped when he told her, at least partly because they couldn't have predicted that an otherwise seemingly typical episode would have such importance.

** 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.

** The first season episode "Shoot" is 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]].

* ''Series/TheMandalorian'' has "Chapter 6: The Prisoner" which, by the end of Season 1, was the only episode to not have any connection to the show's continuity. However, once Season 2 came around, a major character from "The Prisoner" reappeared to help rescue Grogu near the end of the season, gaining this own character arc and being the first human in the show to see the titular Mandalorian take off his helmet.

** "[[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]].

* ''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.

** One episode features a jokey subplot in which Marshall is unable to have sexual fantasies about women other than Lily without first imaging an intricate scenario in which Lily dies of an unspecified disease and gives him her blessing to move on once she is dead. [[spoiler: The widely-reviled ending of the show featured something similar, with the Mother dying of an unknown illness and Ted's children enthusiastically giving him the blessing to go after Aunt Robin years after the fact. Given that this ending was filmed between the first and second seasons, it's highly likely that the Marshall-Lily plot was completely intentional foreshadowing.]]

** The early episode "[[Recap/SupernaturalS01E04PhantomTraveller Phantom Traveler]]" which appears to be a straight MonsterOfTheWeek episode with the brothers having to exorcise a demon who causes planes to crash ForTheEvulz. Not only do we learn later in the season that [[spoiler: the one who killed the boys' mother and Sam's girlfriend is also a demon]] but demons become the major threat for the next few seasons with the rise in demonic possessions being a major plot point.

** Season 1's "House of the Rising Sun" appeared to be a standalone episode mostly intended to fill in the back story of Jin and Sun at first. Its B-plot included the discovery of two skeletons that [[SomethingWeForgot weren't even mentioned after that point until season 6]], but which turned out to be major figures in the island's history.
** Sometimes the writers themselves didn't realize how important an episode would be until later, as was the case with Season 2's "One of Them", which introduced Henry Gale a.k.a Ben Linus, originally intended as a recurring character who would die after a few episodes, but who went on to become the BigBad for the next season and a half, and who remained crucial to the show's mythology even after completing a HeelFaceTurn later on.
** Season 3's "Tricia Tanaka is Dead" is mostly a light-hearted comedy episode about Hurley, Sawyer and Jin fixing an old van Hurley finds in the woods, but the van turns out to be an important ChekhovsGun in the season finale and the skeleton of "Roger Workman" foreshadows a major flashback storyline.

** Season 1's "House of the Rising Sun" appeared to be a standalone episode mostly intended to fill in the back story of Jin and Sun at first. Its B-plot included the discovery of two skeletons that [[SomethingWeForgot weren't even mentioned after that point until season 6]], but which turned out to be major figures in the island's history.

** 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]].