Iconic Item: Sokka's boomerang and club. Katara's necklace, water pouch and "hair loopies".
This is why Aang has to destroy his staff at the beginning of Book 3.
Idea Bulb: Sokka gets an idea - there's an audible ding, and the shot pulls back to indicate the light over his head...which also is the vehicle for his idea to use lamp oil.
Idiosyncratic Episode Naming: Every episode title card has been "Book: Element (Season) — Chapter: Title (Episode)". The title cards have also remained consistent with a white background and detailed border (The sole exception is season 1, episode 3, "The Southern Air Temple", which superimposes the title over the sunrise rather than a white card.)
Idiot Ball: After learning that "Three female warriors from the island of Kyoshi" have arrived at Ba Sing Se, none of the Gaang bother to actually speak to them face-to-face. Justified for Aang and Sokka but not for Katara, who was actually staying at the palace to help plan the invasion. This Idiot Ball later leads to the failure of the Invasion in "Day Of The Black Sun".
Zuko had a pretty firm deathgrip on his up until the third season, anyway. He does things he knows are stupid, and is always shocked when his plans backfire.
Ursa held onto this at one point in "The Search". Knowing Ozai was monitoring her letters, she lied and said that Ikem was Zuko's father out of spite. Which was rather idiotic since it put both Ikem and Zuko's lives at risk. In retaliation/revenge, Ozai attempted to assassinate Ikem and abused Zuko horribly.Nice job thinking this through Ursa.
I Have My Ways: In "The Blind Bandit", Katara is asked how she got information from two uncooperative boys and replies suggestively, "A girl has her ways." Cut to the two boys covered up to their necks in ice.
Impairment Shot: The Shirshu in "Bato of the Water Tribe" after Sokka has the sisters and Katara overwhelm its scent-sight with perfume.
"Zuko Alone" has Zuko's vision fading in and out of focus due to hunger and lack of sleep.
Also, scenes of Toph (and later Aang) "seeing" through earthbending use an impairment-shot-like format, showing the characters in greyscale with expanding rings depicting vibrations from people's movements.
We get another one when Zuko goes into his Angst Coma.
And another when Combustion Man, woozy from a smack by Sokka's boomerang, tries to target the Gaang.
Inevitable Waterfall: In "The Waterbending Scroll". Aang and Katara actually manage to stop the ship from going over, but the pirates in Zuko's boat crash into them and send everybody careening over the edge. Good thing Aang got that bison whistle.
Since those same boats had gotten from the shore to above the waterfall, there must have been a lock system somewhere, right?
Injury Bookend: Aang is injured in the finale of season two, and unable to enter the avatar state. In the season three finale, he runs into a rock directly on the spot he was injured, unlocking his avatar state again.
In the Blood: Zuko, revealed by Iroh in Season 3, has inherited his paternal great-grandfather Sozin's "evil" and his maternal great-grandfather Roku's "good".
"Evil and good are always at war inside you, Zuko. It is your nature, your legacy."
On the other end of the spectrum, Azula seems to have inherited her insanity from her father's side of the family.
Averted in "The Northern Air Temple". Teo might be an excellent pilot, but this is never suggested to be because he is paraplegic, nor does anyone seem to consider him in any way unusual. The only notice anyone takes of Teo's handicap is when Sokka is impressed by his "glider chair".
Similarly, Toph's blindness is never treated as a reason to pity her… and the writers are not afraid to lampshade her blindness with good-natured ribbing by other characters or Toph herself.
Especially Toph. She's so good at it, references to her blindness are more hurtful to other characters than they ever could be to her. Such as when Aang and Katara are mocking Sokka's drawing of Appa, and Toph comes to his "defense":
Toph: It looks just like him to me. Sokka: Thanks, I worked really- Why do you feel the need to do that?
In fact, shortly after Toph joins the group, she must get over her trouble understanding that people can want to do nice things for her because they like her, rather than the pity over her disability that characterized her relationship with her parents.
Inspired By: A number of things in the show are inspired by examples from real-life Asian cultures. However, some things come from other sources.
In "The Blue Spirit", the idea of sucking on frogs for medicinal purposes very likely traces its origin to real-world toads such as the Colorado River toad, which secrete a psychoactive hallucinogenic venom through their skin. In the 1970s, rumors were widely propagated of hippies and other teenagers sucking on or licking these toads to get high; but these rumors were never found to be true. Also, the practice would not actually work for humans, because the human digestive system cancels out the venom… it would have to be injected, inhaled, or smoked in order to have an effect. (This is apparently not true for dogs, however.)
One could also take it as a Shout-Out to an episode of Family Guy that Mike and Bryan worked on.
In "The Northern Air Temple", Sokka and The Mechanist's idea of adding the scent of rotten eggs to the gas to identify the source of the leak is similar to the real world process of adding ethanethiol to otherwise odorless LPG to make it detectable for humans. In fact, many of the Mechanist's inventions are inspired by real life. People told time with grooved candles before clocks (albeit not ones with gunpowder spaced along the fuse); hot air balloons have similar vents to those proposed by Sokka.
In "The Desert", Sokka and Momo's "quenchiest" cactus-juice-induced Mushroom Samba can be traced to a commonly known fact that all cacti collect water - excellent for quenching a desert traveller's thirst in a pinch. Less commonly known is that many cacti contain poisonous or psychoactive substances such as mescaline. Everyone's heard of Peyote, and now you know it's a cactus. And Knowing Is Half the Battle.
Instant Armor: Frequently used by earthbenders, usually out of ordinary rock. Aang did it with snow in the first season finale (as a joke), with crystal in the second, and Toph did it with a metal door in the third. Both have also used the normal rock variation at least once. Curiously, Toph's only use of the rock version, while training Aang in "Bitter Work", left an opening for her eyes (which she doesn't actually use for anything).
In the Artbook, Toph's Rock Armor only had a hole on her mouth/nose, for breathing. It was a mistake of the animation crew.
Due to the compressed time frame of the show, not a whole lot of time was dedicated to showing the characters train. Katara and Sokka in particular seemed to pick up waterbending and swordfighting extremely quickly, often over the course of a single episode. Aang is sort of an exception given that he doesn't exactly master any of his skills until the very end, and he has the advantage of having mastered all the elements a thousand times before in his past lives. Likewise, Toph had already mastered earthbending before she even met the Gaang, and Zuko is shown steadily progressing in his firebending over the course of the series.
Katara is something of an exception as well, during Season 1. Although she masters waterbending instantly in time for the finale, that was only after she got a teacher. Over the course of the whole first season, what waterbending she knows, she teaches herself, and there is a very clear and steady progression from Katara trying hard just to bend a fish out of water in the first episode, and Katara actually putting up a fightnote Which she eventually lost. against Pakku, the most powerful waterbender in the world.
Even though characters may take some time mastering bending, they invariably instantly learn the physical motions involved, even if they haven't mastered the Full-Contact Magic part of the forms. Characters often learn complex routines after seeing it just once.
Inverse Law of Sharpness and Accuracy: In the first two seasons, Sokka hits quite a few mooks with his club and boomerang. After he gets a sword in season three, the only thing he cuts is some ropes, lots of things made out of metal, and a melon. This trope also appears in regard to Mai and Ty Lee - Mai uses knives, and specialises in not hitting the actual person. Ty Lee, on the other hand, fights unarmed and is very good at knocking out and paralysing her opponents. Also, Zuko's broadswords have never touched human skin, but he doesn't have a problem with slamming people against walls, or lifting them with one hand on their necks. Also, his elaborate, deadly looking punches and kicks never seem to make the target.
Aang is free to whack people with air blasts, rocks, and such, and Toph is free to smack people about with rocks, but Zuko's fire attacks always seem to JUST miss and Katara's sharp icicles never seem to connect unless she's just using them to pin someone in place by their clothes.
People slamming against hard surfaces are all over the show, yet seemingly no one gets a broken skull or snapped spine. And all surfaces are completely flat, even in a jungle or a forest where branches would offer plenty of impalement opportunity, people end up slamming against the bole. The only impact on a pointy object is in the series finale.
Unexpectedly averted for Jet. He gets hit once by an earth attack that looks like it would knock a person out at most by the show's standards, but reality comes to play instead and it causes enough internal trauma that he dies despite Katara's healing powers.
Averted in the case of Azula's lightning, which is repeatedly demonstrated to be near-lethal and extremely difficult to block.
Ironic Echo: When Katara gives her stern, and threatening, lecture to Zuko in 'The Western Air Temple', her speech almost completely mimics the ultimatum which Avatar Roku delivered to Fire Lord Sozin a century earlier, to within a few words of being verbatim. Especially toward the middle.
Mai's name means "Smile". She's pretty much played as a Goth who finds everything boring.
Irony: Near the end of the show, shortly after doing it, Iroh comments that he always dreamed of conquering Ba Sing Se. He then comments that he never imagined that in doing so, he was actually liberating it from Fire Nation rule.
It Sucks to Be the Chosen One: Happens to Aang several times throughout the series, though a few standouts are when he returns to the Southern Air Temple in Season 1 and in Season 2's finale when he discovers that in order to control the Avatar State he has to give up his love for Katara.
It Was a Gift: Katara's necklace, from her grandmother by way of her mother. Also, "The Avatar State" opens with a gifting scene reminiscent of (and slightly parodying) Galadriel's gifting of the party in The Lord of the Rings.
It Will Never Catch On: In The Promise, Iroh invents boba tea and has Zuko and Aang try it, only for them to immediately spit it out.
Fire Lord Sozin, though he at least regrets some of his actions and wasted a fair portion of his life on a wild goose chase.
The pirates, who nearly killed Zuko, got paid for it, and are never seen again afterwards.
Kick the Dog: When Zuko and Iroh are refugees in the Earth Kingdom, they are shown kindness by a woman named Song who invites them home for dinner. Afterwards, she has a heartfelt talk with Zuko about how the Fire Nation's war has severely hurt her and her family. In his storm of confused feelings, Zuko...steals Song's family's ostrich horse.
"The Ember Island Players" contains a lot of this.
In the 12th episode, "The Storm", Sokka wakes up with a "What's happening? Did we get captured again?" He's lampshading the fact that the party has collectively been captured in four episodes already, and individual members have been captured far more than that.
Any discussion of field trips with Zuko in the last half of the third season.
The Gaang is baffled and disturbed at the existence of a plain old, non-mix-and-matched bear.
Large Ham: Princess Azula can Chew The Scenery like no one else, managing to turn even the most mundane activity into epic, dramatic supervillainy.
Azula: *after a game of beach volleyball* Yes! We defeated you for all time! You will never rise from the ashes of your shame and humiliation!
Last Minute Baby Naming: Ying and Than, the expectant couple whom Aang helps in The Serpent's Pass, don't name their baby until she is born. The child, Hope, becomes one of the few characters in the show with a non-Asian name.
The Blue Spirit theme plays whenever Zuko goes lurking around in his alter ego, or even just the mask hanging on the side of a peddler's cart trundling by.
The song Iroh sings at the start of "The Waterbending Master" becomes the leitmotif for Sokka and Yue's love theme.
Leaning on the Fourth Wall: The poster for the Ember Island Players' production of "The Boy in the Iceberg" (itself a reference to the first episode of the show) is a thinly-disguised version of the Season 1 DVD cover.
Leave the Camera Running: Minor example, but there's a lot of scenes that keep going for two or three seconds after the action is finished, typically focusing on the characters acting fairly mundane, such as Zuko, left behind when his uncle and another White Lotus member have a secret meeting, standing looking bored before sniffing a flower.
Le Parkour: Aang uses airbending and earthbending to get an edge on this. Zuko just wall-runs the old fashioned way to avoid a spike trap.
Like Father, Like Son: Sokka has exactly the same offbeat sense of humor as his father (remarked upon twice: in "Bato of the Water Tribe" and "The Guru"), as well as the same knack for invention and leadership skill. (What he does not have is his father's knack for public speaking.)
An older Sokka is seen in a flashback Korra has after the first series has ended. At the age of forty-three, Sokka had fully developed the art of public speaking and was as good at giving convincing speeches as his father was.
Zuko averts the trope with his father (at least, his biological one), though Azula plays it straight.
Lightning/Fire Juxtaposition: lightning-bending is a form and result of fire-bending that applied the techniques of it's elemental opposite water. Zuko and Azula fit the Foil aspect of this trope best, as Lightning generation requires an absence of emotion and peace of mind, which reflects pretty nicely Azula's cold an calculative nature, whereas Zuko used (at least at first) rage as a source of power for his firebending.
Lint Value: Aang, who only has three copper pieces, tries to haggle with a pirate who is selling a waterbending scroll for 100 gold pieces. He offers one copper piece. Then, okay, how about two copper pieces? (He gets kicked out of the shop.)
Little Miss Con Artist: Toph proves quite adept at this in "The Runaway", and eventually draws Katara into it as well.
Living Lie Detector: Toph... although it turns out not to work well on Azula. She's also only able to tell whether or not the person believes what they are saying, so she can't tell if a brainwashed person is telling the truth or just what they've been programmed to believe.
The reason her ability doesn't work on brainwashed people or Azula is because it works like a real lie detector- by detecting physical signs of anxiety (ex. increased heartrate) that most people have when they lie. In real life, people who believe that what they're saying is the truth (brainwashed) or psychopaths whose lying doesn't cause them anxiety (Azula) generally pass lie detector tests with flying colors. Which makes this an example of Shown Their Work.
Limited Wardrobe: Subverted and played straight. The kids have a variety of outfits depending on where there are, what they're doing, and what season it is, but if they can get away with it they'll just wear the same thing for as long as possible before being forced to change.
The Load: Impressively averted with Sokka, at least until he Took a Level in Badass. Despite having no powers, few specialized skills, minimal fighting ability and not that much more intelligence than the others, he's a surprisingly useful member of the group. "Sokka's Master", where this is lampshaded, could have gone like this-
Sokka: I feel so useless! Katara: Remember that time you saved hundreds of villagers from being drowned by terrorists? Sokka: Oh yeah!
Locked in a Room: Subverted: Katara and Zuko get trapped in a cave, but no moral is learned and no loyalties change.
Although, it did serve as a one step forward two steps back event. Katara's budding trust for Zuko is crushed (and she holds it to him for a long time), while Zuko's loyalty changes from his uncle to his father and sister.
Loophole Abuse: While standing on a platform with an elderly Earth King, Aang is presented with a really strong looking warrior and a very deadly looking assassin and told he must choose an opponent from the people on the platform. Aang chooses the elderly king. This turns out to be a mistake as the elderly Earth King turns out to be one of the strongest earthbenders Aang has ever met.
Played with in the episode where this fact is revealed, when Iroh tells Zuko to study the history of his great-grandfather and see what he can learn from it, Zuko undertakes a detailed study of the life and times of Fire Lord Sozin, but it doesn't have the end of Sozin's story. When Zuko complains at Iroh about the wild goose chase, Iroh basically says, "No, you idiot, your other great-grandfather" and drops the bomb.
MacGuffin: The frozen frogs in "The Blue Spirit" were mostly a method to separate Aang from the group and give the episode a race against time.
Machiavelli Was Wrong: "I love Zuko more than I fear you.", which follows the trope, but not Machiavelli's teachings. While he taught that if you can't both be feared and loved, fear is more effective as a control mechanism, he made it clear that you should not do anything that makes your subjects hate you. Azula failed this when she tried to make Mai kill Zuko, and again when she was going to kill Mai in front of her best friend, Ty Lee. This prompted their Heel-Face Turn and started Azula on the way to her Villainous Breakdown and ultimate defeat.
Only Zuko's Heel-Face Turn wasn't prompted by love (no matter what Zutarians will tell you)—instead, it interfered with his canonical love relationship.
Magic A Is Magic A: Even though bending isn't exactly realistic with the way it portrays elements behaving, it is at least consistent.
However, spirit-related magic and other things are more mystical and less consistent. Sokka lampshades this on several occasions when Weird Stuff happens (he has no problem with bending, but doesn't believe in magic).
Magic Is Mental: Subverted. The mechanics of bending are never clearly explained, but while mentality has a certain part in it, physical motions are also necessary, as pinning someone's arm can prevent them from bending.
Magitek: The use of bending as industry and as a proxy for modern technology. The Fire Nation still has some very advanced technology in comparison to what the rest of the world is using, though.
On the Day of Black Sun, the Water Tribe submarines used a combination of machinery and waterbending to get where they were going. Same with the Earthbender tanks, which were a flexible design moved by bending the earth under them.
The first licensed game revolved around a character called "The Maker" who created multiple steampunk robots that each were designed to replicate the powers of a particular kind of bender. Culminating in a monster tank called "The Ultimation", which could mimic the powers of Water, Earth and Firebending all at once.
Earthbending is used as a form of locomotion, allowing many Earthbending cities to have a fully working metro system and an efficient mail-delivery system by bending rock trains across rails and boxes made of stone through chutes. Likewise, the development of much of the Fire Nation's tech is based around applications of fire, namely hot air balloons are powered by fire benders heating up the air, while their tanks are little more than steam-powered bunkers on wheels, with the "gunners" being fire benders shooting from portholes.
Becomes increasingly important after the TV series ends and progresses into The Legend of Korra.
Malfunction Malady: Aang's sneezes launch him 10 feet into the air, though he may be doing this on purpose (and explicitly does so at one point).
Mama Bear: Ursa. Katara, the Team Mom, has moments of this (her threats to Zuko in Season 3).
Manchurian Agent: The brainwashing done by Dai Li is activated by saying "(name), the Earth King has invited you to Lake Laogai." to which they respond by gaining Mind-Control Eyes and saying "I am honored to accept his invitation."
Manipulative Bastard: Azula, who likes to lampshade her ability to read people (which doesn't work quite as well as she thinks) and uses it to her advantage, notable examples being the way she played Long Feng, and telling her father that Zuko killed the Avatar so that, if it turned out Aang were still alive, Zuko would get the blame. She learned everything she knows about manipulation from her father, Fire Lord Ozai. There is a reason that just about everybody in the show has their life affected by the guy, even though most of it is offscreen.
Martial Pacifist: Iroh. He only fights when he has to, but when he does, it's clear that he is one of the most skilled characters on the show.
Market-Based Title: Avatar: The Legend of Aang in the UK, where "bender" is derogatory slang for a male homosexual.
Master Of All: The Avatar is expected to become this: a master of all four elements in a setting where it usually takes a lifetime of training to become a master of just one. Aang takes this Up to Eleven when he becomes the first Avatar to also learn the lost art of energybending.
May-December Romance: Played with. Aang is technically over a century old, but is physically and mentally in his early adolescence. Additionally, Katara is visibly at least a year or two older than Aang, growth and maturity-wise. This makes Avatar: The Last Airbender one of the few shows to showcase a romance where the woman is the older partner.
Maybe Magic, Maybe Mundane: Aunt Wu's fortunetelling is presented as this in the Season 1 episode "The Fortuneteller." Although the Aesop is that your future isn't set and you need to take responsibility for it, all of her predictions that we see play out come true. This is lampshaded at the end by the old man from the beginning of the episode.
Meaningful Echo: It's easy to miss, but in the episode "Avatar Day", Sokka suggests Aang break out of jail, demonstrating by yelling "Airbending SLICE!" Two seasons later, in the finale, Sokka decides to take down the airship fleet with an "Airship SLICE!"
Zuko: I don't need luck though, I don't want it. I've always had to struggle and fight and that's made me strong. Its made me who I am.
The Missing Faction: There are four people, of which Water, Earth and Fire remain. The three of them used to live in harmony with one another and with the Air Nomads, but the Fire Nation attacked everyone and exterminated the Air Nomads.
Sokka, especially when he was played by Jackson Rathbone in the live-action film adaptation.
Mix-and-Match Critters: Started off for fun by Bryan Konietzko, but it wasn't long before the writers caught on. Now he and the character designers are mostly trying to keep up with their own ideas. Lampshaded when it was mentioned a certain character wanted to exhibit his bear. The characters who weren't reading the announcement immediately assumed Katara meant some hybrid animal.
May also apply to some vegetables, like tomatocarrots.
Momma's Boy: Zuko, far from being in a My Beloved Smother relationship, loves and misses his mother very much, and thinks of her constantly when he begins to question what would be the right thing to do.
Mondegreen: Wait, so Aang's old Master among the Air Nomads was named Monkey Atso?
Monochrome Apparition: In the episode "The Spirit World", when Aang accidentally transfers himself into the Spirit World, he's shown as completely blue and translucent.
Mood-Swinger: Katara, to the point of a meme about how "it must be her time of the month."
Doubly interesting due to waterbenders' close connection to the moon.
Zuko is also quite the mood swinger (See "The Warriors of Kyoshi" for a great example.)
Mood Whiplash: In "Tales of Ba Sing Se", the sorrowful Tale of Iroh is followed up immediately by the funny Tale of Aang.
Within the Tale of Iroh itself. Most of it is Iroh being his usual funny/awesome self (stopping his own mugging by giving a mugger career advice, calming a baby, playing with some kids), with only the last 30 seconds or so where it turns sad.
The main action stories of Book 3 ("The Day of Black Sun" and "Sozin's Comet") are both preceded by fluffy episodes ("Nightmares and Daydreams" and "The Ember Island Players").
The Season 2 Finale is quite a whiplash. The heroes lose the deciding battle, Azula gains control of the most powerful earthbenders in the Earth Kingdom, Zuko betrays Iroh, and Aang not only permanently lost the Avatar state, he also died for a good few hours.
Subverted in "The Tales of Ba Sing Se", Iroh is threatened at knife point by a mugger, and the audience expects him to open up a can of unholy whoop-ass on the mugger. At first, Iroh lectures him about his poor stance, then lightly knocks him to the ground while taking his knife. What makes it a subversion is that he then gives the knife back and corrects the mugger's stance, which almost borders on Fridge Logic when you consider he's essentially giving advice on how to more effectively mug people. Fortunately, he turns around and remarks "but to tell you the truth, you do not look like the criminal type" and then proceeds to make him tea and give him advice on turning his life around. For his part, the mugger is excited about this because no one has ever believed in him before.
Played straight by Zhao in The Siege of the North: he knew that the Moon Spirit was a vulnerable and harmless Koi fish and that he could destroy waterbending altogether by killing it. After he does, the Ocean Spirit took exception to his act by becoming Koizilla (cue Oh Crap and being too busy crapping himself to try and run for his life).
Mundane Made Awesome: Shows up a few times, usually played for comedy. For instance, the EmberIslandPlayers' fight scenes consist mainly of actors jumping around and throwing streamers at each other, but the music is the same as or similar to what it was in the scenes they're based on.
In a flashback showing parts of Roku's life, Sozin leaves Roku to die when the latter accidentally inhales toxic fumes from an erupting volcano.
In the season one finale, Zuko considers doing this to Admiral Zhao when the latter is attacked by the (giant, enraged) spirit of the oceans. After a moment's consideration, he holds out a hand to save Zhao, but the admiral refuses to allow his rival to save him, and is swept away to (presumably) his dead.
Toph is a perfect example of this. She is a pre-pubescent girl, she's short, and she has no muscles. She faces the Boulder in battle, a large, muscular man, and in only a few swift movements she defeats him. (NOTE: Most Earthbenders are shown to be large muscular men, in fact very few female earthbenders are shown in the series.)
Mushroom Samba: "Cactus Juice; it'll quench ya." Also an example of Truth in Television: all cacti concentrate water, so most (including Sokka, a freakin' Eskimo Fictional Counterpart) believe that it can be easily extracted by desert travelers in need. What most don't know is that cacti also concentrate poisons and/or hallucinogens to deter herbivores (which Sokka and Momo found out). Ever heard of Peyote? Now you know that it's a cactus.
The whole episode "Nightmares and Daydreams".
Sokka spends most of "The Blue Spirit" sick and delirious.
Also Combustion Man, Koh the Face Stealer, and Long Feng (which means "dragon phoenix" in Chinese, and also sounds like "long fang"). Wang Fire deserves brief mention as well.
The Napoleon: Chin the Conqueror from "Avatar Day" - possibly justified as he was only short in comparison to Kyoshi, who was huge.
A Nazi by Any Other Name: The Fire Nation was heavily inspired by Imperial Japan, which conquered almost all of the islands in the Pacific and launched several invasions into China, eventually becoming one of the Axis powers in WWII.
Never Say "Die": Averted with everyone that died before the series started, as well as death threats. On the other hand the fate of the three named characters that died during the show was systematically pussyfooted around (though all three were confirmed by Word of God). They even managed to lampshade the ambiguity without actually saying that the characters died.
That said, it's also played with in one very specific case. While talking with his previous incarnations about how to not kill Ozai, they heavily insinuate that he must but never outright *say* he has to kill Ozai. That's because it turns out he doesn't have to.
Politically destabilizing Ba Sing Se may have felt right, but it was a very, very, bad idea.
Then a few episodes later, Katara sees Zuko serving tea and instantly runs to inform the authorities. If she had investigated further, confronted him herself or thought about the situation for more than a second, Zuko never would have been put in a position to turn to Azula's side to begin with. (And Aang probably would have finished his last chakra.)
Nice Job Fixing It, Villain: In the finale, Ozai manages to break through Aang's protective shell and proceeds to slowly walk towards him, ready to finish him off. However, all he managed to do was unblock Aang's seventh chakra, allowing him to enter the Avatar State. Much asskicking ensues.
Ozai has a second helping of this that deserves a medal for just how astoundingly long it takes to come around and bite him, compared to just how much it does. The simple act of banishing Zuko provides Aang with an extremely powerful ally without which Aang never would have learned Firebending, let alone True Firebending. Even before the heel face turn, how many times has he -saved- Aang from someone else because of his obsession with being the one to bring him in.
The Nicknamer: Toph, and also Sokka. Lampshaded with "Leave the nicknames to us, honey."
Ninja: Inverted. The play in "The Ember Island Players" features authentic Japanese theater-style stagehands dressed in the all-black outfits that inspired the theatrical version of the ninja's costume.
Characters dress in ninja-style outfits for infiltration a number of times in the show: Zuko in "The Siege of the North", Zuko and Katara in "The Southern Raiders"...
Zuko's "The Blue Spirit" persona is a ninja in all but name.
Ninja Log: Zuko pulls this in "Lake Laogai" as part of an Indy Ploy to gain access to the Dai Li's headquarters.
Non-Lethal Warfare: Somewhat averted by the fact that lots of violent death is explicitly mentioned, though never shown on screen.
Several Professional Wrestlers in "The Blind Bandit", most obvious "The Boulder".
The Earth King heavily resembles Puyi, the last Emperor of China. Like Kuei, Puyi was made emperor at a very young age and was a puppet emperor during his early childhood and later under the Japanese occupation. Puyi was also trapped for years inside the Forbidden City, similar to how the Earth King never left the palace. The Earth King also wears spectacles, like Puyi did, and clothing based on the Chaofu, ceremonial clothing of the Manchu emperors of the Qing Dynasty.
Non-Indicative Name: The geographical feature "The Great Divide" in the episode by the same title is the Avatarverse equivalent of the Grand Canyon. The "Great Divide" in the real world is exactly the opposite: the North American mountain range that divides the Pacific and Atlantic watersheds.
Non Sequitur: Expect Sokka's dialogue to consist primarily of this when he's sick or under the influence of cactus juice.
The time Sokka got two fishhooks stuck in his thumb note he tried to get the first fishhook out with another fishhook.
What exactly is "Love Amongst the Dragons" about, and how did the Ember Island Players "butcher" it?
The event that kicked of the Gan-Jin/Zhang rivalry
From "The Warriors of Kyoshi":
Katara:No, Appa! Don't eat that!
Iroh's journey to the Spirit World.
"Miyuki, did you get in trouble with the Fire Nation again?"
No One Could Survive That: After Aang's apparent death by lightning in the second season finale, Zuko claims, "There's no way he could have survived"... but he's lying, and the Dangerously Genre Savvy Azula knows this. He actually did die, but Katara revives him with the spirit water.
Not So Stoic: In "The Invasion," Sokka realizes that Azula is baiting them, and tells everyone to just leave and ignore her. "IGNORE!" Then she tells him about how she's been keeping Suki prisoner, and Suki was always convinced that Sokka would come to save her, which he never did... He loses it.
Not Wearing Pants: Aang's most humiliating nightmare in "Nightmares and Daydreams". At the end of the episode, he turns it around on the dream version of Ozai.
In the trip to Kiyoshi Island. Just before they arrive, Katara is mending Sokka's pants. He makes a snarky remark about women and she refuses to fix them. He states that he needs them! Without missing a beat, Aang responds "Don't worry Sokka! Where we're going, you won't need pants!" Thus they arrive on the island of the women warriors.
Not Worth Killing: What Katara decides in regards to Yon Rha, her mother's killer, in "The Southern Raiders."
Now or Never Kiss: Before he sets out to play his part in the Invasion on the Day of Black Sun, Aang voice his concerns that he might not survive to to Katara- and then kisses her before he flies off. It's Aang's First Kiss too( Katara's first kiss was with Jet, according to the Avatar Extras on the episode named after him.)
Iroh in "Sokka's Master" acts like a broken man slobbering for what food he can when people are looking. When alone, he is working out big time.
King Bumi pretty much all the time. He even encourages this tactic to Aang, wanting him to think outside the box.
Obfuscating Stupidity: Iroh since the start of the series. We know that he's a wise, respected general and a master firebender, but we often wonder why. It's also quite easy to forget that he's the Fire Lord's elder brother.
And King Bumi is seen to be more crazy than stupid. There apparently is a difference.
Suki: I lost someone I care about. He didn't die. He just went away. I only had a few days to get to know him, but he was smart, and brave and funny. Sokka: Who is this guy? Is he taller than me? Suki: No. He's about your height. Sokka: Is he better looking? Suki: It is you, stupid!
A more physical example would be the entire gang minus Suki and Toph, when they went to see the Ember Island Players. Most were in denial even when rather similar depictions could be spotted in the acting.
Offing the Offspring: Ozai almost did it to Zuko when he was 10, and tried to do it again in "The Day of the Black Sun."
Offscreen Inertia: The last we ever see of Azula is her being chained to a grate, completely insane and screaming in despair. While Word of God stated that Azula was committed to a high security asylum, it's not actually shown in the series proper.
Also, Toph's earthbending teacher and the hired mercenary were never seen again after Toph locked them in a metal box together.
Offscreen Moment of Awesome: Iroh's escape from the Fire Nation prison in Season 3 was never seen (although there was plenty of action in the invasion arc already). We're just told he was a One-Man Army. And this might have even happened during the eclipse, when he couldn't firebend. This is largely why the fans consider him so awesome.
Oh Crap: Whenever anyone is stupid enough to provoke Aang into the Avatar State, this is usually their feelings in general as they realise what they're in for.
During the series finale, the look on Ozai's face during his fight with Avatar-State Aang says it all.
Actually even before Aang regained his Avatar state, Ozai had pretty much the same look when he thought that Aang was going to serve up his own lightning right back at him using the redirect he had learned from Zuko. Ozai stopped using lightning for the rest of the fight.
To really put things into perspective, that's the Oh Crap look on the face of the world's most powerful firebender who's also gooned on the juice of a hundred suns.
The Ojou: Mai, and Toph might fit. She at least acted like one before she revealed her skills to her family.
Old Master: Bumi, Iroh, Pakku, Gyatso, Roku and others. Also the entire frikkin' Order of The White Lotus.
The second part of the four-part series finale, which has emphasis on the White Lotus, is even named this.
One-Woman Wail: Happens during the last episode, when Sokka and Toph are about to die. And during the penultimate episode. And almost every time the show goes into slow motion, e.g something awesome is happening.
Ozai attempts to invoke this when "giving Zuko advice" (read: trying to corrupt him) in the sequel comic "The Promise", claiming that whatever the Fire Lord decided was right by definition.
Justified (though not specifically killing) by Iroh, who explains that while he's the only other firebender who might be capable of defeating Ozai, history would look at him doing so not as an act to restore peace and balance (the Avatar's role in the mortal world) but as one brother killing another for power. Their aims at the end may be overly optimistic - we know things went wrong in the past, they will do again - but under the circumstances emphasising the Avatar's duty was probably the better way of handling things.
The Only One Allowed to Defeat You: In the first season, Zuko needs to capture Aang to regain his honor, and will go as far as invading a prison and breaking Aang out when somebody else from his nation catches him.
In fact he fights Azula over this very point in "The Chase."
Mentioned in a way when Zuko confronts his father during the solar eclipse: while both of them are temporarily bending-less, Zuko is armed with his broadswords. Ozai asks why Zuko doesn't just kill him right then and there; he responds by saying that that is the Avatar's destiny, not his.
Also stated by Iroh in the finale, where he says that while he could potentially defeat Ozai, he can't, because the Avatar is the generally recognized arbitrator. According to Iroh, if he kills Ozai, the world will simply see it as a brother killing a brother for control of the throne, while if the Avatar defeats Ozai, it will be seen as a restoration of balance.
Katara: "Water. Earth. Fire. Air. Long ago, the four nations lived together in harmony. Then everything changed when the Fire Nation attacked. Only the Avatar, master of all four elements, could stop them. But when the world needed him most, he vanished. A hundred years passed, and my brother and I discovered the new Avatar — an airbender named Aang. Although his airbending skills are great, he has a lot to learn before he's ready to save anyone. But I believe Aang can save the world."
Opposed Mentors: Katara and Toph have very different opinions on how Aang should be trained. Katara, his waterbending teacher goes for the soft, encouraging, positive attitude, while Toph, his earthbending teacher, prefers the rougher, blunter, drill sergeant style. This culminates in an interesting mud-fight scene between the two.
This happens to Sokka when Momo grabs a spider out of his mouth to eat it.
Momo is missing, and Sokka thinks Appa ate him, so he crawls in Appa's mouth to see. Appa just spits him out.
Orphaned Punchline: At one point Zuko tells Iroh's favourite joke. Trouble is, Zuko can only remember the punchline.
"Leaf me alone, I'm bushed!"
Orphan's Plot Trinket: Although she's technically only half an orphan (her father is still alive, but off fighting a war in another part of the world), Katara's grandmother's necklace functions as this on a couple of occasions: lost on a prison platform, found by Zuko, used to track the band by scent, retrieved by Aang; revealed Katara's grandmother's history with the Northern Water Tribe and the man who becomes Katara's waterbending master.
Overly Long Name: In "The King of Omashu", while disguised as an old man, Aang identifies himself as "Bonzu Pipinpadaloxicopolis III", and says that Katara and Sokka are his grandkids. Katara then immediately says her name is "June Pipinpadaloxicopolis". Somehow, she manages to pronounce the name exactly the same way, as does the king.
Overly Polite Pals: Aang and Sokka briefly in the episode "The City of Walls and Secrets", as they are trying (and failing) to behave like high society folk.
Perfect Pacifist People: The Air Nomads were a great example of this, having no army and preaching peace and harmony. But they could still fight if needed. When you see Monk Gyatso's body, he is surrounded by the remains of Fire Nation soldiers.
Person of Mass Destruction: Some benders, more often than not earthbenders, can be quite destructive. And a fully realized Avatar is like this with all the elements... and that's before they go into the Godlike Avatar State.
Personality Powers: Bending is easier for people with certain dispositions. Earthbenders confront their problems head-on, firebenders tend to be angry/passionate, etc. This is why Aang has such a hard time learning earthbending as he did not like direct confrontation.
In another flashback-heavy episode, we see Zuko befriend a young boy, even going so far as to give him a dagger that has quite a lot of sentimental value. This makes it that much more heartbreaking when the boy rejects Zuko after finding out he's a firebender.
Pietà Plagiarism: Katara holding Aang's lifeless body after Azula "kills" him in the Book 2 finale.
Pillar of Light: When Aang gets released from the iceberg after 100 years. This is what alerts Zuko to his awakening.
Repeated in a Meaningful Echo at the end when Aang succeeds in taking away Ozai's bending in the finale.
Pinned to the Wall: This is Mai's primary combat tactic, due to the fact she's a specialist in throwing daggers in what is ostensibly a kid's show. Rather than hit the squishy humans, she usually pins their clothes to whatever is behind her victim (or the attack gets blocked altogether).
Pirate Parrot: In episode 9, The Waterbending Scroll. It's one of the things that tips off Sokka that the "merchants" the Gaang is interacting with are pirates.
Phlebotinum Battery: Waterbenders are at their peak under a full moon. Firebenders are at their normal peak under the sun. When a comet passes through the atmosphere it supercharges the firebenders' abilities, which is a major plot point throughout the series.
Physical Scars, Psychological Scars: Zuko's father issues are represented physically through the scar over his eye, and Zuko suffered both as part of a confrontation with his father. The connection between the two is even discussed in-universe, when Katara laments that she didn't get the chance to heal the scar because it may have helped clear up his emotional issues as well.
And Aang, who thought it was cool at first, until he learned better.
Plot Parallel: Several, most obviously in "The Great Divide" and "Bitter Work". The whole series can be considered one with Aang's and (most prominantly) Zuko's parallel Coming Of Age Stories.
"The Storm" and "The Avatar and the Firelord" are both also examples of this same character parallel.
Politically Incorrect Villain: Zuko, though only in the first season, when he's the most outright antagonistic. In particular, he calls both Katara and Sokka "peasant" as an insult on several occasions.
To say nothing of Azula's last (coherent) line: "There you are, filthy peasant!"
Posthumous Character: Monk Gyatso, Avatar Roku (And by extent, every other avatar except Aang), Fire Lord Sozin, Fire Lord Azulon, Lu Ten, and Kya.
Potty Dance: An unnamed Water Tribe boy does this in the second episode.
Power Glows: Again, Aang when in the Avatar State. In the second season premiere, Roku explains that the glow is the combined power and experience of every Avatar that came before him being channeled through his body.
Sokka: How did you guys get out [of the caves]? Aang: Just like the legend says, we let love lead the way. Sokka: Really? We let huge, ferocious beasts lead our way.
The Power of the Sun: Firebending is much stronger during daylight hours than at night, and firebending is completely disabled during the solar eclipse. The true firebending practiced by the Sun Warriors follows the power of the sun even more.
In Season 1 when Haru's father is about to throw the warden of his prison overboard.
Warden: Please, no! I can't swim! Haru's father:Don't worry, I hear cowards float.
Iroh's "Did I ever tell you how I got the nickname 'the Dragon of the West'?"
The Precarious Ledge: The Serpent's Pass is a long, narrow ledge across the body of water separating the main land from the city of Ba Sing Se. Because the Gaang and a pair of newlyweds cannot manage to buy the ticket for the ferry, they went here instead. Not only navigating here is already hard, there's a freaking giant water serpent that lives here, trying to knock them off the ledge.
Princeling Rivalry: Apperance wise Iroh is the larger good hearted brother and Ozai is the plotting evil younger brother who tries to use Iroh's moment of weakness (his only son dying) to persuade their father to pass over him for succession. Some shady business later, their father dies, and his dying wish is exactly what Ozai asked for. Slightly subverted in that though Ozai is a schemer and has a smaller frame, he's at least Iroh's equal in power if not slightly stronger.
While she is smaller, and a schemer, and evil, Azula is also stronger than her older brother Zuko who should be Overlord Jr., but is instead a Token Good Teammate to his evil family and rightful heir. Azula never really indicates that she has designs on the throne for herself until Zuko does a Heel-Face Turn and leaves the family and its about to be handed to her, but she always made sure that if anything went wrong in the family Zuko would get the blame from the beginning.
Princess for a Day: Katara and Toph in "City of Walls and Secrets", of the non-royalty variety. Somewhat subverted with Toph, who actually is a member of a very wealthy and prominent family, but was posing as someone else.
Prison Episode: The show seems to enjoy using this trope, perhaps because the show is about fighting a totalitarian state:
Season 1 has "Imprisoned", where Katara deliberately gets herself imprisoned by the Fire Nation in an attempt to free friend from said prison. It's a specially designed prison for Earthbenders, a steel rig out in the middle of the ocean so there's nothing for them to bend (except coal from the engine room).
Season 1 again "The Blue Spirit", where Aang is captured by the Fire Nation.
Season 3 has "The Runaway", where Toph and Katara end up in jail, and "The Boiling Rock", where Zuko and Sokka infiltrate a Fire Nation prison.
In the "Puppet Master" episode, Hama tells the gang how she, and the other water benders from the Southern Water Tribe, were rounded up and taken prisoner by the Fire Nation. There, they were kept in cages, with their hands shackled, so they couldn't bend. The warden even pumped in dry air as an added measure. And while they were given food and water, it only enough to keep them alive, but just barely. Clearly a POW Camp of the Hell Hole Prison variety this time for Waterbenders.
Another similar prison camp completing the trio of the earthbender rig and the waterbender camp is a Firebender camp called the Boiling Rock, given two episodes "The Boiling Rock Part 1 and 2." Rogue firebenders are put into giant coolers that temporarily freeze their ability to bend. Also hailed as the most ruthless and efficient prison in the Fire Nation. There probably would've been an airbending prison had they not wiped them all out.
Prison Rape: Defied. In "The Boiling Rock: Part 1," a female guard catches Zuko (disguised as a male guard) loitering in the female prisoners' block, seemingly standing watch for a buddy. The female guard silently glances at Suki's cell before demanding Zuko let her check inside.
Pro Bono Barter: At one point, Sokka takes an odd job, and rather than getting paid in coin as he was expecting, he got handed a large, wet, dead fish.
Prodigal Hero: Zuko was forced to leave home, but otherwise fits here.
Prophecy Twist: Iroh mentions that when he was young he had a vision of himself taking down the walls of Ba Sing Se, which he believed meant his destiny was to conquer it. It is only in the finale that he realizes he wasn't meant to take over the city as an invader, but to liberate it from the Fire Nation.
Punishment Box: In "Boiling Rock", the titular prison has "The Cooler", a small refrigerated cell designed to contain fire benders.
The Purge: A century before the start of the series, Fire Lord Sozin massacres the Air Nomads, largely in hopes of killing the new Avatar. (Unbeknownst to Sozin, Aang was frozen underwater in his Avatar State and thus remained unharmed.) As the series draws to a close and Sozin's Comet returns, Sozin's grandson Fire Lord Ozai attempts an even larger-scale massacre of the vast and powerful Earth Kingdom, with the ambition of thereby becoming ruler of nearly the entire world.
Sokka's one-episode pet Hawky, was never seen again. At the end of the episode Toph and Katara attempted to send a letter to Toph's parents. It is likely that the Hawk was either intercepted, never reached its destination, or never returned once the Gaang relocated. Either way Toph's mother and father never reappears, nor does Hawky.
Putting on the Reich: Toyed with and subverted. In the first season, the Fire Nations uniform is very Mongolian in design and visually defines them as the show's villains. The uniforms are shown to be but one design of many as the culture itself opens up and they and the people wearing them are given a bit more depth as the series progresses.