History WalkingSpoiler / LiveActionTV

** Season 5 has Adrian Chase, Star City's district attorney, who later during the season turns out to be Prometheus, the BigBad of the season, and the illegitimate son of a CorruptCorporateExecutive that Oliver killed all the way back in Season 1. His goal is to break Oliver and show him that he [[PoisonousFriend poisons everyone he comes in contact with]].

* ''Series/ChouseisinSeries'':

** Season 3: Arthur Claypool, Harold and Nathan's other friend and the creator of Samaritan. Diane Claypool/Control

* The main focus of Sophia in ''Series/TheWalkingDead'' is about her being lost and turning into a walker.

* ''Series/Legacies'': The very existence of the show, with Hope Mikaelson as the central character, spoils that something bad must happen to the majority of the characters in ''Series/TheOriginals'', as her parents and extended family would never let her face danger on her own if they were around to protect her.

* ''Series/StrangerThings'': Vecna is introduced as the BigBad of Season 4. However, it's hard to talk about him without eventually bringing up that he's an alter ego of One, who in turn is an alter ego of Henry Creel.

* ''Series/TheOfficeUS'': Pam's ex-boyfriend Brian is in the film crew documenting Dunder Mifflin.

* ''Series/{{Life}}'' had Rachel Seybolt, who was adopted by the man who killed her family.

* ''Series/RussianDoll'': Alan being stuck in the GroundhogDayLoop with Nadia.

** Iwan Rheon was told to tell nothing of his character in the third season, who is merely called "Boy" in the script, and he is the only new actor playing a big part that was not part of the promotional material before the season began. ''Everything'' about the character's identity, allegiance, aims and procedence is meant to be a mystery and the clues given by the show are intentionally contradictory. Of course, this being the case is a spoiler already because it means that viewers can't take for true any personality he goes by until then. Those who have read the source material know who he is, but the character's introduction was massively changed and his true identity is only revealed on screen in the season 3 finale.
** And now in season 4, the Night's King made his appearance. Though HBO would try to RetCon his existence on their site, referring to him as "another White Walker".

* ''Series/ResurrectionErtugrul'': So much as even mentioning the name [[spoiler: Sugay]] cannot be brought up unless one mentions [[spoiler: Halime’s untimely death after giving birth to Osman]] near the end of the fourth season.
** Another season 4 example would be [[spoiler: Almila/Alangoya]]. Where to begin? [[spoiler: First, she only shows up after Ertugrul slays Kopek, who appeared to be the only other antagonist (Besides the Tekfur of Bilecik) left for him to defeat for the past few episodes]]. Then, [[spoiler: we find out that she’s Noyan’s sister, and that her big sibling had actually survived his supposed defeat season 2]].
** A season 5 example, meanwhile, would be [[spoiler: Arikbuka, the final antagonist that Ertugrul comes face-to-face with in the series]]. Not only is he never brought up prior to his introduction late into the season, but so much as trying to bring the character into a discussion would require mentioning [[spoiler: that he revived Beybolat/Albasti after the latter leaped off a cliff in order to prevent Ertugrul from executing him]].

** Ash Tyler is actually Voq, Klingon spy with a pretty terrible case of SplitPersonality activated by a Klingon TriggerPhrase. The fact that this is the case was hidden even during production--a pseudonym was used for Voq's actor and Shazad Latif was [[LyingCreator tied to a different Klingon]] during production. Ash Tyler looks human, acts human, and even ''scans'' human enough that specialized Starfleet tests designed to catch TheMole fail to detect two personalities, though Dr. Hugh Culber notices a few physical abnormalities. [[spoiler:This [[HeKnowsTooMuch costs him]] [[NeckSnap his life]].]]

* ''Franchise/MarvelCinematicUniverse'':
** ''Series/AgentCarter'':
*** Dottie Underwood is introduced as just Peggy's new neighbor, but turns out to be a DarkActionGirl and a prototype ComicBook/BlackWidow to boot.
*** In a similar vein, Dr. Ivchenko, who is actually the BigBad and the [[Franchise/MarvelCinematicUniverse MCU]] counterpart of Dr. Faustus.
** ''Series/AgentsOfSHIELD'':
*** Grant Ward was introduced as TheBigGuy and a ReplacementFlatCharacter for the team, but turns out to have some ''[[TheMole serious]]'' HiddenDepths. And that's only the beginning - in fact, trying to describe him at any point after the first two-thirds of Season 1 '''will''' give something away.
*** Agent Garret, who turns out not only to be [[BigBad The Clairvoyant]], but is also responsible for Ward becoming a member of HYDRA and is also the first [[LegacyCharacter Deathlok]].
*** Skye's mother Jiaying, who serves as the FinalBoss of Season Two ''after'' she is revealed to be NotQuiteDead.
*** Skye herself qualifies as well, since she's [[CanonCharacterAllAlong actually]] the MCU version of ComicBook/DaisyJohnson, aka Quake.
*** A large part of [[FriendOnTheForce Glenn Talbot]]'s entry is spoilered out due to a twist late in Season 5, where [[FaceHeelTurn he]] [[CompositeCharacter becomes]] [[KnightTemplar Graviton]].
*** Nathaniel Malick has [[WeHardlyKnewYe very little characterization in his first appearance]]. Pretty much everything else about him ties in to the MidSeasonTwist in the seventh season, where he cheats death via CosmicRetcon, acquires superpowers through PlayingWithSyringes, and generally goes from a bit part in his brother's story to one-half of the BigBadDuumvirate.
** Elektra in ''Series/TheDefenders2017''. Just the fact that she's alive following her apparent death in ''Series/{{Daredevil|2015}}'' says something, and there are more twists along the way.
** The IGH assassin in season 2 of ''Series/JessicaJones2015'', who turns out to be Jessica's mother Alisa.
** In ''Series/WandaVision'', Wanda's nosy neighbor Agnes, who is [[CanonCharacterAllAlong actually]] [[AdaptationalVillainy a villainous]] Agatha Harkness. On a lesser level, the Quicksilver that appears... only it's seemingly the one from the Film/XMenFilmSeries... and then, that he was part of Agatha's scheme.

** At first, it seems like Will Reeves was created for the series. Then came "This Extraordinary Being", he was revealed to be Hooded Justice, a character who was ShroudedInMyth in the original comic -- and that Hollis Mason's InUniverse speculation in the original comic was [[AdaptationalBackstoryChange oh]], [[AdaptationNameChange so]] [[SparedByTheAdaptation very]] [[AdaptationalSexuality much]] [[RaceLift wrong]] [[AdaptationalNationality in]] [[AdaptationalJobChange this]] [[AdaptationalHeroism series]].
** Cal Abar, who also seemed to be created for the series was revealed in "An Almost Religious Awe" to be be an amnesiac Dr. Manhattan.

* Michael and Lincoln's mother, Christina Scofield, in ''Series/PrisonBreak''. Season 1 shows us her funeral in a flashback, and season 2 goes out of its' way to establish that she was a good, devoted mother, mainly to contrast with their father who walked out on both of them at a young age (despite [[DaddyHadAGoodReasonForAbandoningYou having a good reason for it]]). And then along came season 4, which not only reveals she's alive, but she's also an EvilMatriarch and the final BigBad.

*** Mitsuzane "Micchy" Kureshima undergoes a massive FaceHeelTurn, going from Kouta's SecondRider and little brother figure to being TheHeavy of the show's third story arc, [[LoveMakesYouEvil all out of an unrequited crush on Mai]]. He even [[TheQuisling sides with the Overlords]] and (apparently) [[CainAndAbel kills his own brother]] in pursuit of his goals. Even the fact that his brother survives and Micchy is given the opportunity to redeem himself at the end of the series are spoilers.

** The other two seasons have each had a villain like that. Peter from Season 1 initially appears to be a vegetable in an intensive care facility (having hidden the fact that he's been slowly healing himself), whilst Jennifer from Season 3 initially appears to be an {{Adorkable}} HotTeacher, only revealing that she's the mass murdering dark druid who's been kidnapping and sacrificing people all season.

** Cal Abar, who also seemed to be created for the series was revealed in "An Almost Religious Awe" to be be amnesiac Dr. Manhattan.

** It has has multiple characters in its second season whose very existences spoil the reveal that the singularity created portals to Earth-2, the biggest of which being Jay Garrick and Earth-2's Harrison Wells. Even before the end of Season 1, it became increasingly hard to talk about Dr. Wells without major spoilers, and nigh impossible to refer to his alter-ego, the Reverse Flash. (And that's not even mentioning the existence of the ''original'' Harrison Wells, whom Eobard Thawne [[KillAndReplace killed and replaced]].) Basically, trying to talk about any character on this show played by Tom Cavanagh is like navigating a huge minefield made of spoilers.

* ''Series/MrRobot'' has the titular character. He's a pretty important character throughout the first season, but we never learn any personal details or even his name until the end of the season. Then come the last few episodes, and surprise, he's a subconscious manifestation of Elliot's dead father Edward Alderson, and no one else sees or hears him, so ''every scene he's been in'' didn't happen the way we, or Elliot, thought it did.

** As of season 4, we have Elsa from ''Disney/{{Frozen}}''.