Tropes A to H (Chekhov's Gun) | Tropes I to P | Tropes Q to Z (Ship Tease, Shout-Out, Shown Their Work, Wham Episode)
Fans have become incredibly familiar with, and wary of, this trope, as apparently nigh-on everything in the show eventually comes back as a major plot point later on:
- Katara's necklace, which she explains is her mother's only memento.
- Zuko would later claim the necklace and attempt to bribe Katara with the promise to return it in exchange for Aang. When that fails, he uses its scent to track down the heroes with the help of June's shirshu.
- When the gang goes to the Northern Water Tribe, it is only after seeing Katara's necklace that Master Paku realizes that she is the granddaughter of his first love, for whom he made the necklace. This in turn causes him to change his mind about teaching Katara waterbending, her knowledge of which is essential in the rest of the series.
- In the first episode of the second season, Katara is given an amulet of water from the North Pole oasis, which she is told has unique properties. This becomes very important in the season finale, in which it's used to bring Aang back to life after he is mortally wounded by Azula.
- One of the scrolls in Wan Shi Tong's library mentions Lion Turtles. In the finale, one such creature teaches Aang how to energybend, thus providing the hero with the only technique capable of ending the war without further bloodshed.
- The Fire Nation is shown developing war balloons in the first season. This becomes critical in the final season, where the vehicles are used to turn the tide of battle during the Day of the Black Sun, enabling the firebenders to defeat and capture the entire invading forces save Team Avatar. The balloons are also employed during the finale to transport the villains to the Earth Kingdom, thus setting in motion Ozai's plan to scorch the land.
- Katara's waterbending scroll is what allows Katara access to the Library in a later episode.
- From the start of "The Waterbending Scroll," they set up a Chekhov's Gun that really plays out only if you're really paying attention closely. Iroh mentions he lost his Lotus tile and remarks that a certain strategy he uses often revolves around it. At the time, you assume he's being the bumbling old man he's been since the show started. Fast-forward to Season 2, where he sits down to play Pai Sho with an old man and uses the White Lotus Gambit, which the old man recognizes and sets up his board accordingly. The result? The old man and Iroh create the sigil for the Order of the White Lotus, who serve the purpose of sneaking Iroh and Zuko into Ba Sing Se. The lotus tile makes another reappearance, as Pian-Dao leaves one for Sokka after Sokka's apprenticeship is completed, and in the end, the Order of the White Lotus makes a reappearance as the army set to reconquer Ba Sing Se in Season 3. This was a use worthy of Harry Potter!
- A minor one in "The Avatar State," Zuko and Iroh cut off their top-knots with a knife Zuko has on him. The same knife is given a history as a present that Iroh claimed from a surrendering Earth Kingdom general at the start of the Siege of Ba Sing Se. Fittingly (and ironically) the blade is engraved with "Never give up without a fight."
- In the first season's finale, Admiral Zhao mentions a library hidden "deep beneath the sands" in his youth, where he learns how to kill the Moon spirit. Aang and his friends, in turn, unknowingly find the same library in the second season, and learn how to defeat the Fire Nation: by attacking the Fire Nation capitol on The Day of Black Sun.
- Zuko's swords, seen hanging on the wall in the first episode, eventually become his weapons of choice as the story progresses; unfortunately for him, it is this signature dual-wielding style which allows Zhao to uncover the truth that Zuko is The Blue Spirit.
- Iroh's sandal. Zuko finds while looking for him in the first season. Used in the last episodes to track Iroh using Jun's beast, after Zuko reveals he had it all this time.
- Toph's bracelet/piece of meteoric iron. She missed the time it would be really useful because she didn't have it on her, but it served a mildly useful purpose an episode later (picking a lock). In the graphic novels, Toph also learns she can use it to find new metal benders.
- In an early season one episode, Katara and Sokka get sick, and Momo is sent to fetch water. He brings back piles of random junk instead. One of these items is a crown with two dragons facing each other. In season 3, Aang and Zuko find the secret society of Sun Warriors, with two dragons that perform a 'dance' that ends in the exact position shown on the crown.