History EarlyBirdCameo / WesternAnimation

* Multi-Paul, [[spoiler:Dupli-Kate's twin brother in [[ComicBook/{{Invincible}} the comics]]]], appears as a prisoner in episode 3 of ''WesternAnimation/Invincible2021''.

* ''WesternAnimation/TheLegendOfKorra'' shows future BigBad and WellIntentionedExtremist Kuvira appearing during a metalbending dance routine halfway during Book 3, after which she receives some minor speaking roles. She's not named until the season's penultimate episode, where her introduction coincided with a ScareChord that instantly foreshadowed her future villain status in the show's final season.

* ''WesternAnimation/TheVentureBrothers'' uses this form of the trope regularly. Many easily-missed background characters gain major plot relevance down the line. Sometimes it's only a few episodes later (such as the Investors appearing in the background of an episode before their official introduction,) while other times it's many ''seasons'' later (such as August St. Cloud, who was a frequent background character dating all the way back to season 1, but wasn't officially introduced until season 5.)

* ''WesternAnimation/InfinityTrain'':
** Our first glimpse of [[spoiler:[[BigBad the Conductor]]]] is in the [[Recap/InfinityTrainS1E5TheCatsCar fifth episode]]... unless you were paying [[FreezeFrameBonus extremely close attention]] in [[Recap/InfinityTrainS1E1TheGridCar the first one]]. In which case, [[spoiler:you can see [[SamusIsAGirl her]] [[https://i.imgur.com/tiVcMex.jpg disappearing behind some trees]] when Tulip first wakes up in the snowy car]].
*** Actually, no. What can be seen briefly in the first episode is not [[spoiler:the Conductor]] but is actually a [[https://infinity-train.fandom.com/wiki/Passenger_Transportation_Pods Passenger Transportation Pod]].
** The [[Recap/InfinityTrainS1E10TheEngine season one finale]] briefly shows other train passengers on a computer display, including two [[BrokeTheRatingScale whose numbers extend beyond five digits]]. The pair, [[TheCorrupter Grace and Simon]], later appear as [[spoiler:secondary antagonists in Book 2]], in addition to being the main characters of Book 3.

* Long before viewers even learn who [[TheDragon Princess Azula]] is in ''WesternAnimation/AvatarTheLastAirbender,'' she makes one brief appearance; she's seen in the audience during Zuko and Ozai's Agni Kai, in which the former receives his signature facial scar. Since she's the only one in the crowd ''smiling'' as Zuko screams in pain, the viewers are given a clear warning that she is ''a serious threat'' - [[HeroKiller and she very much lives up to the warning]]. She also appears in the opening theme as the firebender, albeit cast in shadow as a silhouette.

* ''WesternAnimation/TheDickTracyShow's Go-Go Gomez made his first appearances in two ''WesternAnimation/MrMagoo'' shorts prior to the series: "Requiem for a Bull" and "Fuel in the Sun". He is referred to by his full name in both.

* ''[[WesternAnimation/TheDickTracyShow]]'s Go-Go Gomez made his first appearances in two ''WesternAnimation/MrMagoo'' shorts prior to the series: "Requiem for a Bull" and "Fuel in the Sun". He is referred to by his full name in both.

* In the ''WesternAnimation/LegionOfSuperHeroes'' cartoon, before he joined the Legion and coined his superhero name in The Substitutes, Matter-Eater Lad was a competitor in the Space Olympics episode "Champions." The other, rejected [[WhatKindOfLamePowerIsHeartAnyway lame-power applicants]] also showed up in Lightning Storm for comic relief. Ultra Boy makes his first appearance as a competitor in Champions, as well.

* ''WesternAnimation/JackieChanAdventures'': Well before Tarakudo officially appears in Season 4, his face is first shown in Season 2, in the form of his MarkOfTheBeast on the cover of the Demon Archive which turns Jade into the Queen of the Shadowkhan for an episode. The same mark is shown in Daolon Wong's cauldron when the dark chi wizard summons the Ninja Khan to serve him (it's the latter spell gone wrong that directly brings Tarakudo into the fold in the Season 4 premiere).

* Odd case involving a song: The ''WesternAnimation/TeenTitansGo'' episode "Waffles" features background music that eventually became [[PottyDance "The Pee Pee Dance"]] from "Serious Business". Though it might be downplayed, as the creators have stated that [[ExecutiveMeddling the show's creative executives did not take well to some concepts in the original script]], so it might have originally been planned for Season 1, with the instrumental here being planned as a ContinuityNod.

** Before being a heroic sheriff on the ''WesternAnimation/MagillaGorilla'' show, Ricochet Rabbit was an antagonist on an episode of ''Touché Turtle'' two years earlier.