History ChekhovsGunman / WesternAnimation

* ''WesternAnimation/TheVentureBrothers'' practically runs on this trope. At the end of season one, The Monarch's cocoon base is destroyed. It is rebuilt surprisingly quickly at the start of season two, and this is {{handwaved}} by having Monarch say he used parts he stole from an unknown character named Sargent Hatred. At the end of the season, Hatred makes an appearance at The Monarch's wedding, but it's essentially a one-off gag. Shortly after that, in the episode that reveals Billy Quizboy and Phantom Limb's shared backstory, the shouty, red-haired NCO who demotes Brock to Operation: Rusty's Blanket is shown putting on a Guild of Calamitous Intent signet ring, revealing that he is, in fact, Sergeant Hatred, before he got his distinctive tattoos. Then in season three, Hatred becomes Dr. Venture's new arch-enemy, and it turns out his entire motivation for doing this is to get back at the Monarch for stealing from him (by stealing Monarch's nemesis.) This leads directly to Hatred becoming the new Venture bodyguard and a main character in season four.

** The crazy old inventor, Fiddleford Mc Gucket, has played a huge role in the past, being the best friend of Stan[[spoiler:ford]] Pines.

** Evagelyne's younger sister Cleophelia made a {{cameo}} near the end of Eva's dream sequence in Episode 20 of Season 1 before she receives her first proper mention in Season 2, Episode 17, and makes her actual appearance as the Brotherhood of the Tofu's SixthRanger in the following episode.

* In ''WesternAnimation/TeenTitans'', [[GodOfEvil Trigon]] has a minor appearance in the first season episode "Nevermore". He shows up again in the fourth season as the BigBad, commanding the loyalty of the previous BigBad and preparing TheEndOfTheWorldAsWeKnowIt.

* In ''WesternAnimation/YoungJustice'', the audience is introduced to Barbara, a minor student at Artemis' school who has only one line of dialogue in the entire first season. At the start of season 2, she's joined the main cast as Comicbook/{{Batgirl}}.

** The [[Recap/MyLittlePonyFriendshipIsMagicS1E1MareInTheMoon pilot episode]] introduces Applejack's little sister Apple Bloom in passing during the extremely crowded Apple Clan reunion. Later on, there's a brief shot of her with two other fillies. Later in the season, Apple Bloom plays a key role in the events of "[[Recap/MyLittlePonyFriendshipIsMagicS1E9BridleGossip Bridle Gossip]]", and gets the spotlight in "[[Recap/MyLittlePonyFriendshipIsMagicS1E12CallOfTheCutie Call of the Cutie]]", which ''also'' officially introduces the other two fillies, Scootaloo and Sweetie Belle, the latter of which is Rarity's little sister.
** Big Macintosh and Granny Smith from the family reunion; the former seems well on his way to becoming a regular.
** When Twilight first arrives in Ponyville in the series premiere, a pink mare gasps and bolts. Turns out she's bolted to organize a welcome-wagon party, and [[EstablishingCharacterMoment thus Twilight (and the audience) are introduced]] to Pinkie Pie.
** An episode-specific example: "[[Recap/MyLittlePonyFriendshipIsMagicS2E18AFriendInDeed A Friend in Deed]]" introduces a donkey named Matilda early on. She turns out to be Cranky's lost love.
** Near the beginning of "[[Recap/MyLittlePonyFriendshipIsMagicS3E11KeepCalmAndFlutterOn Keep Calm and Flutter On]]", Discord casts a spell that causes a group of beavers to become mean-spirited and they later appear near the end and build a dam that causes Sweet Apple Acres to flood.
** In the beginning of the very first episode, Twilight rather roughly turns down an invitation to a party hosted by Moondancer because she'd just read a book warning that Nightmare Moon might be returning to Equestria that night. Just a moment meant to [[EstablishingCharacterMoment establish]] Twilight's asocial nature? Well, yes, but then in Season 5 we meet Moondancer, and it turns out Twilight's rebuff of her invitation really affected her. The plot of ''Amending Fences'' is about getting her to come out of the shell she retreated into because of Twilight's refusal.
** All of Starlight Glimmer's previous quick background appearances throughout season 5 tie together in [[Recap/MyLittlePonyFriendshipIsMagicS5E25TheCutieRemarkPart1 The "Cutie Remark"]] [[Recap/MyLittlePonyFriendshipIsMagicS5E26TheCutieRemarkPart2 two-parter]]. [[spoiler:In "Amending Fences", she saw how one missed event soured Moondancer on the idea of friendship. In "What About Discord?", she overheard the suggestion about using time travel to witness an event that had been missed. Finally, in this episode, Twilight recounting how the Sonic Rainboom brought the Mane Six together gives Starlight the information she needs to potentially stop their friendship before it ever starts.]]
** [[AvertedTrope Averted]] in ''[[Recap/MyLittlePonyFriendshipIsMagicS4E26TwilightsKingdomPart2 Twilights Kingdom Part 2]]'', bordering on subverted for some viewers. Scorpan helped defeat Tirek in the first place, so one would expect Celestia to send Twilight to... Not look for him. Or even mention asking him for help at all. Odd.
* In the ''WesternAnimation/OverTheGardenWall'' episode "Schooltown Follies", an anguished schoolteacher named Miss Langtree, seemingly abandoned by her boyfriend Jimmy Brown, is greatly distressed to find that there is a gorilla on the loose wreaking havoc on the school. At the end of the episode, it is discovered that [[spoiler: the wild gorilla was just Jimmy in a circus costume he couldn't get out of. He never meant to leave Langtree permanently, but went to join the circus so he could earn some money for a ring to propose to her with]].

* A similar accidental example, though not in the same series, can be found in ''WesternAnimation/TheRenAndStimpyShow'', which had a character named George Liquor, who had a starring role in the episodes "Man's Best Friend" ([[MissingEpisode kept off of Nickelodeon]]) and "Dog Show", as well as some cameo appearances here and there. Creator/{{Nickelodeon}} didn't like the character, and gave the rights to him to Creator/JohnKricfalusi once he is fired from the series' production. George Liquor has starred in his own webseries since then, which is currently getting a revival.

** In the episode "The Creeps", Finn gets freaked out by this terrifying ghost-creature. By the end of the episode he assumes it was a prank by his friends, but they swear they don't know what he's talking about, and its never explained. It later turns out [[spoiler: its a vision from a past life, trying to send him a message]].

** Two major villains, [[spoiler: The Lich and GOLB,]] first appear in brief glimpses before they become villains; one as a past conquest of the hero Billy, and one at the end of the concept episode ''Puhoy''.

* ''WesternAnimation/AvatarTheLastAirbender'': In the episode "The Storm", you see a younger girl standing close to Iroh and ''smiling'' as Zuko gets scarred in the Agni Kai. This lets you know two things: One, she's family, and two, she's gonna be ''trouble'' when she finally shows up. Ladies and gentlemen, you just met [[HeroKiller Princess Azula]].
** Even before that, she was [[EarlyBirdCameo the firebender in the opening]].
** Azula is just one of many examples; the show ''loves'' this trope. [[spoiler:The Giant Lion-Turtle who finally unlocks the EleventhHourSuperpower for Aang]] was mentioned as early as the pilot, appeared several times as a statue, and showed up on a suspiciously conspicuous scroll in the ancient library.
** The regular opening of ''WesternAnimation/AvatarTheLastAirbender'' has a bender for each element. The airbender is Aang. The waterbender is Pakku, who wouldn't show up until episode 18. The firebender is Azula, who wouldn't [[ChekhovsGunman be seen]] until episode 12 and wasn't properly introduced until episodes 20 and 21. The earthbender was meant to be Toph, but Toph was changed into [[CuteBruiser a small girl]] by the time she actually appeared (though the model was [[DevelopmentGag reused for the Boulder and Roku's earthbending teacher, Sud]]).
** June appears as an apparently one-shot bounty hunter character, but becomes crucial to the plot in [[spoiler:the finale, where she helps Zuko and the rest of the gang find Iroh and the Order of the White Lotus]].
** The two koi fish in the pond that Aang stared at when meditating into the Spirit World in part 1 of "The Seige of the North" turn out to be the Ocean and Moon Spirits, as Aang realizes when speaking with Koh.
** In its SequelSeries, ''WesternAnimation/TheLegendOfKorra'', Kuvira, the primary antagonist for the fourth and final season, actually makes several small cameos throughout Book 3 as a seemingly random Zaofu solider, though she was an important ally to Korra in the Book 3 finale.

* In several old ''WesternAnimation/LooneyTunes'' and Creator/TexAvery shorts, a silly little character who [[RunningGag keeps walking by on every other scene]] is revealed at the end to be the hero.

** The two koi fish in the pond in part 1 of "The Seige of the North" turn out to be the Ocean and Moon Spirits, as Aang realizes when speaking with Koh.

* In the ''WesternAnimation/OverTheGardenWall'' episode "Schooltown Follies", an anguished schoolteacher named Miss Langtree, seemingly abandoned by her boyfriend Jimmy Brown, is greatly distressed to find that their is a gorilla on the loose wreaking havoc on the school. At the end of the episode, it is discovered that [[spoiler: the wild gorilla was just Jimmy in a circus costume he couldn't get out of. He never meant to leave Langtree permanently, but went to join the circus so he could earn some money for a ring to propose to her with]].

* ''Franchise/ScoobyDoo'', as a comedy/mystery series, makes heavy use of this trope; most renditions of the franchise following ''WesternAnimation/ScoobyDooOnZombieIsland'' often [[LampshadeHanging lampshade]] or avert it; but they'll still be surrounded by episodes that do it straight.
** Typically, if there's more than one suspect, whoever is the most polite and helpful is the crook.

* ''TheSimpsons'' has both a gunman and a gunwoman.