The Rough Rhinos from Season 2 are a minor example. They feature in multiple episodes, but don't get any real characterization. Each one specializes in a different kind of combat. They're also, apparently, a great singing group.
Aang has to master all four elements before Sozin's Comet arrives.
Also during "Day of the Black Sun" The Resistance has to take over the citadel before the eclipse is over and the fire benders gain their power back.
Rage Breaking Point: Invoked by a general hoping Aang's Avatar state would be useful. Aang has good reason to fear what would happen, and the general's fortress gets devastated when Aang is finally set off.
Ragnarok-Proofing: Subverted. An ancient firebender city looks like it's in perfect shape despite being abandoned for centuries, but it turns out people are still living there.
Ramen Slurp: Master Pakku slurps noodles — and some kind of octopus or squid — while training Aang in "The Waterbending Master".
Randomly Gifted: Bending can travel down family lines, but isn't purely genetic and develops among non-benders.
The Rashomon: "The Great Divide". The real story is actually just made up by Aang, in order to get the people to make peace.
Ready for Lovemaking: In "The Southern Raiders", Zuko wanders into Sokka's tent for a talk and finds Sokka half-undressed and posed seductively in a lovenest of candles and roses, obviously expecting someone else to wander in. Just before that, Zuko had bumped into Sokka's girlfriend trying to sneak into the tent. When we next see Sokka the following morning, he has a floral necklace for no particular reason except to indicate he got "lei'd." And, assuming that Suki gave it to him, that Suki got "deflowered."
According to "Avatar Extras", The Guru Pathik is even older. Specifically 150.
Apparently, Avatar Kyoshi lived to be a record breaking 230 years old. Which is sort of ironic, since people who are large tend to live a lot shorter.
Living Relic: And the Lion Turtle, the largest animal of all, which is far older than the Avatar itself. That's old, considering the Avatar has existed for nearly 10,000 years. It's definitely Older Than Dirt.
Multiple examples - Fire Nation and Water Tribe, Zuko and Azula, the red and blue dragon motif, and Ozai and Aang during the final Energybending scene.
A pair of red and blue dragons shows up at least three times. Within a vision of Prince Zuko, where his inner conflict is represented by a blue dragon (Azula) and a red dragon (Iroh); the mounts of the ideologically conflicted Fire Lord Sozin (blue) and Avatar Roku (red); and finally with the original Firebending Masters. Red/blue is initially used to signal division, but the Masters dance in unison and reveal fire's true dual nature, which plays into Avatar's larger theme that everything is one.
Reincarnation Romance: One debated piece of Fanon is that the Avatar has a circle of companions who are reincarnated beside him/her. There is evidence both for and against this.
The reason Gyatso was so intensely devoted to Aang's welfare is because Gyatso had a literal whirlwind Bromance with Avatar Roku. Given that Roku's Earthbending master, Sud, uses Toph's original character design, it could be considered similar.
On the other hand, However, Roku's Waterbending master was a nameless, voiceless cipher. Ummi, Water Avatar Kuruk's bride that Koh The Face-Stealer claimed, remains Koh's prisoner even in Korra's time. And perhaps most prominently, Roku's wife Ta Min is all over the place - though her character design evokes Katara's Fire Nation disguise and post-war hairstyle, her voice actress, Grey DeLisle, also voiced both Azula and Katara's mother.
Although when Ozai declares himself Phoenix King in preparation for his plan to destroy the Earth Kingdom and ensure total world domination he gives himself a rather more ornate crown/helmet.◊
Religious Russian Roulette: Sokka, bargaining with the powers that be to give up meat in exchange for getting him out of a hole. Meat, AND sarcasm.
Remember the New Guy: A semi-example. When we meet Avatar Yangchen for the first time in the series Aang doesn't seem to know all that much about her, she even had to introduce herself to him. But the comics that continue the story show that Yangchen was super-important in Airbender culture. Even had a holiday named after her, which makes Aang's apparent lack of knowledge about her a bit weird. Possibly justified by the fact that Aang wasn't a very attentive student, relying more on The Gift than anything else.
Residual Self Image: Aang visits Avatar Roku in the spirit realm. While there, Aang has his traditional shaved head and Air Nomad robes, rather than the short hair and Fire Nation disguise he is currently wearing.
Rewarded as a Traitor Deserves: A non-canon example from the card game, but Afiko sold out the Air Nomads to the Fire Nation at the start of the war and was eventually executed by the Fire Nation for his trouble.
Zuko's ship suffering major damage every few episodes — losing the miniboat over a waterfall, a Shirshu ripping a hole in the deck, being buried under an avalanche, being set on fire by a catapult, being struck by lightning, and finally being blown up entirely in a failed assassination attempt by Admiral Zhao.
This gag even continues in the show's successor, The Legend of Korra, where a company called Cabbage Corp. gets shut down by the police and the CEO (seemingly a descendant of the cabbage merchant) cries "NOT MY CABBAGE CORP!"
People forgetting that Toph is blind, and thus can't read or recognize people's faces. This reaches a point where, on two separate occasions in the same episode, someone tries to confront her by "showing" her a piece of paper.
Katara:: Well then, what's this? *pulls out a wanted poster of Toph*
Toph: I DON'T KNOW! I mean seriously, what's with you people?! I'm blind!
Toph has also been known to use her blindness to mock her friends, such as with Sokka's drawings in one scene. After Aang and Katara make fun of Sokka's crude and unrecognizable drawing of Appa, Toph comes to his "defense" and comments "It looks just like him to me!" It takes a second for Sokka to catch on. note "Thanks! I worked really—Why do you feel the need to do that?"
The episode where the Gaang is looking for Appa. At one point they're putting up posters, and suggest Toph tags along with Sokka.
Toph: You think I can't put up posters on my own? *slathers the wall with glue and slams the poster on backwards* ...it's upside down, isn't it? ...I'll just go with Sokka.
Sokka's fake beard and his "skill" with art.
Foaming Mouth Guy!
Starting in Season 1 with King Bumi, every time a character (usually Sokka) tells a bad joke, there is a moment of silence, followed by an off-screen cough. See Chirping Crickets above.
Similarly, some scenes end with Momo intruding, often to grab a bite. These are sometimes called "Momoments".
The fact that nobody other than Aang and Zuko (possibly Zhao) know that the Blue Spirit is actually Zuko. Made especially hilarious in the short "School Time Shipping" when Katara turns down Haru, Jet, Zuko and Aang because she's already got a date to the dance: the Blue Spirit.
Zuko: I did NOT see that coming.
Whenever Zuko and Aang are involved in a fight scene, Zuko hits a wall.
Any real fight involving Zuko has him hitting either a wall or the floor.
Sanity Slippage: Azula, starting when her friends leave her, and accelerating after her promotion to Fire Lord. She rather quickly goes barking mad over the course of the penultimate episode.
Sarcasm Failure: When Toph and Sokka are dangling off an airship, with Sokka's space sword and boomerang gone and things looking bad, neither one of them has anything sarcastic to say. This may be one of the only times in the series that both of them are completely serious.
Every single time the camera focuses on Azula's face, a Scare Chord plays. Though instead of the standard blaring piano keys, she gets a distinct bell-like sound that is a lot quieter and means she's up to something sneaky.
It seems like a modified gamelan...which would sound pretty weird to western ears. But even if you're used to the noise, this one is a little off.
Pretty much any music during her Villainous Breakdown, and the noises she makes when she finally breaks down and cries.
Scarecrow Solution: In the episode "The Painted Lady", Katara starts one of her own. As she helps some villagers, they mistake her for their local deities - and instead of trying to clear up the mistake or at least feel bad about it, she chooses to make the most of it. Of course, the villagers are outraged when they find out that she has deceived them, but they quickly forgive her since they realize that the help she gave them was genuine rather than a part of some manipulative plot. After the whole thing is over, it turns out that the real Painted Lady actually does exist - and she is pleased with Katara's deeds.
Schizo Tech: Done very originally with bending worked into daily life leading to interesting variations from the less technologically advanced Water Tribes to the Steampunk warships and crawlers of the Fire Nation.
Secret Test of Character: Happens to Sokka in episode 4 of season 3. Piandao refuses to train him, but Sokka's humble and sincere statement of needing to be properly trained changes his mind. He then puts him through various tests, such as painting some scenery to utilize his ability to remember details around the battlefield. Later Sokka reveals he's not actually a Fire Nation citizen, which causes Piandao to attacks him, but again was just testing Sokka to see how much he learned. He gives Sokka a white lotus as a parting gift, which is a clue to his role later in the show.
Seen It All: The fortune teller senses that Aang will be in a tremendous struggle for the fate of the world. Aang quickly asks her to skip that and check his love life.
Send in the Clones: "Joo Dee" is not so much a person as it is a job title and the Dai Li have dozens of similar-looking brainwashed women ready to step in and take over should the current Joo Dee ever slip up.
Sequel Hook: "Where. IS. My Mother." Subverted in that while both The Legend of Korra and The Promise acknowledge the hook, neither one answers anything. It took until The Search before this plot thread was finally followed up on.
Serious Business: Azula's reaction to winning a game of, essentially, beach volleyball in "The Beach":
Azula: Yes, we defeated you for all time! You will never rise from the ashes of your shame and humiliation! (pause) Well that was fun.
Sexy Backless Outfit: The Painted Lady, according to the little statue Shu brings out. Katara noticeably averts this by wearing her Fire Nation dress under the robe. The REAL Painted Lady, who appears at the end of the episode, does not.
Ship Sinking: In-story, during "The Ember Island Players": Aang is dismayed to see his and Katara's actors gleefully sink their ship by agreeing to be "just friends", as they were playing the moment that actually was his love confession.
In universe, there was a ton of Ship Sinking done for Zutara during the last few episodes.
Shipped in Shackles: The bounty hunters who captured Toph stuck her in a metal box for transport so she couldn't use her earth bending to escape. Of course, Toph gets out by inventing metal bending. See the CMOA page.
Shock and Awe: Experienced firebenders are able to bend lightning.
Shocking Defeat Legacy: Two examples. One was for the Fire Nation, when Iroh gave up on taking Ba Sing Se after breaching the wall. The other was for La Résistance when Azula's coup meant that said impenetrable city finally fell.
Shoo the Dog: when Suki is forced to get rid of Appa to save him from Azula in "Appa's Lost Days".
Shoot the Dog: Avatar Yangchen, the previous airbender avatar, was a proponent of this, and advised Aang to kill Ozai, claiming that his own spiritual needs would have to be sacrificed for the greater good, because she believes his role as the Avatar supercedes his teachings as an airbender.
Kyoshi has shades of this as well, though not to the same extent as Yangchen. When Aang consults her about what to do about Ozai, she takes responsibility for the accidental death of Chen the Conqueror, claiming that although she didn't kill him, she was prepared to if necessary.
Aang's armor in Sokka's Master calls up a lot of various anime and fighting games, the most notable of which is Nightmare's arm piece and helmet from Soul Calibur. Also worth mentioning from that sequence: Tenchi's "Wind Sword". It's also a Crowning Moment of Funny when all this extra equipment makes Aang fall over backwards.
Combustion man: Strange, stoic killer + guy with tattoos that make things explodenate + guy with mechanical limbs because his original ones were lost in an accident. Fullmetal Alchemist anyone?
In Ba Sing Se, Zuko disguises himself with a mask that's actually Pazuzu, as seen in The Exorcist. However, that film actually used a Japanese hannya Noh mask, which is in fact Asian. Thus, it's the Fantasy Counterpart Culture's equivalent foreign face.
In "Nightmares and Daydreams" Aang has a dream in which Momo and Appa are dressed up as Samurais and fighting each other. Samurai!Momo duplicates the distinctive gestures made by the hero of Kurosawa's Yojimbo.
Jet bears a striking resemblance to Spike from Cowboy Bebop with his hairstyle, laid-back attitude and bent grass stem/cigarette in his mouth. Spike's partner is named Jet too.
Also, the scene in "The Blue Spirit" where Aang asks Zuko if they could have been friends if they met earlier in life is based off a similar scene in the episode "Waltz for Venus" of Bebop.
And that huge rock forest where Aang fights Ozai is called "Wulong Forest" after the currency from Cowboy Bebop... the creators are big fans.
The scene where Zuko, after being hit by Azula's lightning, lies on the ground twitching as lightning continues arcing across his body is highly reminiscent of Return of the Jedi.
Similarly, Guru Pathik and the episode where he appear could remind one of Yoda.
Expanding on this, Aang trains with Pathik, learning the nuances of being The Chosen One... until he gets a vision that Katara is in trouble, runs away from his training to save her, ends up nearly getting himself killed for his trouble and letting the bad guys win. Sound a little familiar?
The scene in Season 3, The Firebending Masters, an idol pops up out of the ground and Aang says "I'm just very suspicious of gems sitting on giant gold pedestals" was a shout out to Indiana Jones.
In the same episode, Prince Zuko wall-runs over a pit of spikes.
The entire part of The Firebending Masters where Aang and Zuko were exploring the temple had a very Indiana Jones feel to it, really.
The barfly that June beats up twice looks strangely similar to Ryu.
In an indirect Actor Allusion, during their Agni Ki in the Season 1 episode "The Storm", Zuko tells his father, voiced by Luke Skywalker himself, "I will not fight you" in the exact same intonation Luke did.
In the episode The Blind Bandit, a couple of rather familiar Earthbenders named "The Boulder" and "The Hippo". The Boulder's a bit of a wrestling twofer, seeing as his name is in reference to Dwayne "The Rock" Johnson, but he acts and speaks more like Hulk Hogan. And is, of course, voiced by Mick Foley.
Fire Nation Man is also a clear reference to Nikolai Volkoff with the use of his Fire Nation flag and his obnoxious national pride.
The two "Siege At The North Pole" episodes are chock full of shoutouts to another animated show about a plot to kill a spirit, Hayao Miyazaki's masterpiece Princess Mononoke.
A scene from "The Blue Spirit", the one where Zuko is knocked out by the impact of an arrow in his (masked) face is nearly identical to one in Princess Mononokewhere San is knocked out by a bullet.
Also from Miyazaki, Appa's six legs are reminiscent of the Catbus from My Neighbor Totoro, being somewhat based off it.
A lot of the spirits - like the swamp monster and Koh - are similar to the designs of spirits from Gibli films, since the creators are big fans of ones like Princess Mononoke and Spirited Away.
The creators are also fans of Gainax productions, particularly Neon Genesis Evangelion. The art book for the show lists Hei Bai's design as being based on the Angels, while the long limbed and hunched look of Bumi's body was inspired by the Evas themselves.
Aang's pushups in The Warriors of Kyoshi, going from using both arms, to one arm, to simply blowing air, are likely a shout-out to Kung Pow! Enter the Fist.
In the episode Avatar Day, Sokka channels Judge Bao, with some Sherlock elements, while attempting to solve the case.
The signal horn that one of the Fire Nation sentries uses when he spots Aang in the episode 'The Blue Spirit' makes a sound precisely identical to the horn sound effect which kicks off the intro of the reality TV series Survivor.
Airbender arrows look a lot like the markings on the head of the Red Tornado.
Ba Sing Se's political landscape is very resembling of 1984's.
When Sokka is throwing around names for the team at the end of The Drill, he suggests "Fearsome Foursome", which was the nickname of the legendary defensive lines of the NFL's Los Angeles Rams in the 60's and 70's.
Listen closely to the banjo music playing when Tho and Due first appear in "The Swamp". It's clearly meant to be reminiscent of "Dueling Banjos" from Deliverance.
The way the airbenders recognize the Avatar's new incarnation is by Aang picking specific toys (which belonged to previous Avatars) out of thousands of possibilities - a practice that mirrors one of the actual ways Tibetan monks find the newly-reincarnated Dalai Lama.
Many of the styles of martial arts used by the benders are based on actual styles. The Book 1 Disc One extras have an interview with Sifu Kisu, describing them.
Waterbending is Tai Chi.
Earthbending is Hung Gar.
Firebending is Northern Shaolin Kung Fu.
Airbending is Ba Gua.
Toph's Earthbending style, which is unique to her, is Chow Gar Southern Praying Mantis.
A rather subtle one, but Toph is blind and was once the, "melon lord" the Blind Melon Lord.
All of the Chinese script in the series says what the characters read. There was an expert in ancient Chinese calligraphy on the staff.
In the episode called "The Northern Air Temple", Sokka meets another Mad Scientist type. They are discussing how to prevent the natural gas from leaking and blowing everyone up, since they can't see or smell it. One of them arrives on a solution of putting rotten eggs in with the gas. Although not quite the modern solution, it's pretty close (they use something with a "rotten egg" smell, called Mercaptan). Some of the other inventions also seem to have sound research.
A tumblr exists to point out how they show their work in such background details as architecture, hairstyles, clothing, foods, furniture...
Shut Up and Save Me!: A restrained-by-pirates Sokka, to Aang and Katara, in "The Waterbending Scroll".
Shut Up, Hannibal!: When Aang is held captive by Zhao, Zhao states that he won't kill Aang, because he would just reincarnate as a new Avatar. So instead, Zhao will keep Aang alive...barely. Aang's response? He inhales and blows a gust of air that completely knocks Zhao on his ass.
"Shut Up" Kiss: Sokka and Suki in "The Serpent's Pass"; Aang and Katara in "The Invasion".
The song that plays when Yue sacrifices herself to revive the Moon Spirit.
Also, the music playing during the final Agni Kai between Zuko and Azula.
Single Palette Town: In fact, single palette continents: Nearly all Earth Kingdom residents wear a green & brown motif, Fire Nationers wear red, Water Tribers wear blue. When there were still Air Nomads, they wore orange and yellow, though being part of a monastic order may have inclined them towards maintaining a similar form of dress.
Averted with the fishing village Gaang comes upon in season 3. Despite being Fire Nation, most of the town wear simple clothes you'd expect of fishermen, mostly tans and light blues.
Sliding Scale of Continuity: The show is mostly like level 4 (Arc-Based Episodic) - while the Gaang is always traveling the world to find bending masters to teach Aang and there are plenty of Fillers that belong on level 3 (Subtle Continuity), there are pretty steady continuous developments on the villainous side that would be very jarring to anyone who just watched individual episodes here and there.
When the White Lotus members take Ba Sing Sae back from Fire Nation rule, they pull down a statue Ozai had had put up of himself.
In the same scene, Iroh burns a Fire Nation flag that had been hung over an Earth Kingdom symbol.
When King Bumi reclaims Omashu on the day of the Eclipse, he defaces an Ozai statue with smiley face bits of stone and then pulls it down.
Smite Me, O Mighty Smiter: "Bitter Work" has Zuko doing this, in hopes that he could practice his new lightning-redirection technique. Unusually for the trope, it's played for drama.
Smug Snake: Admiral Zhao. Seriously, when your Establishing Character Moment is getting your ass handed to you by both a teenager and an old man in the same ten minute interval, you should start considering the possibility that maybe you're not as awesome as you think you are. As "The Deserter" shows, Zhao is a strong firebender, but not at all a skilled one.
Sneaky Departure: In "The Awakening", Aang feels he needs to regain his honor by fighting the Fire Lord alone, and so he sneaks off the ship that the gang is currently hiding out on.
Sniff Sniff Nom: Sokka does this to the slime covering the walls on a cave inhabited by Buzzard Wasps.
Katara: You spent the last day hallucinating on cactus juice and now you're licking something stuck on a cave wall?!
Sokka: I have a natural curiosity.
Snipe Hunt: The terms of Zuko's banishment. Track down someone not seen for 100 years and you can come home again? Right. This is really brought home when Zhao, acting with the full authority of the Fire Nation, immediately moves to prevent Zuko from continuing to hunt him when it becomes apparent that the Avatar actually has returned.
So Unfunny It's Funny: Many of Sokka's weird nicknames and jokes are this. (And apparently so are his father's, according to a comment from Bato when Sokka makes one in Bato's presence.) Apparently the unfunny-is-funny effect holds true for the rest of the gAang as well as the audience, because by Season 3, they have gotten so used to Sokka as a source of humor that they actually miss his jokes when he's off training with his master… and the replacement jokes they try to make are even more unfunny-funny (but only to the audience, not them).
Averted In the finale, Sokka lowers the airship to a safe distance before dropping the crew out of the ship using the bomb bay. Later on, Aang uses waterbending to soften what would otherwise be a very hard crash into a lake from a very long drop.
In "The Swamp" when Sokka, Katara and Aang fall off Appa above the treetops and land in a foot of water, but are totally unharmed when they stand up. Aang cushions his fall with airbending, Katara might have done something subconsciously, but Sokka is magically fine without it.
In "The Kyoshi Warriors" when Aang is tossed away by the Unagi when it first shows up. The rather splat-like sound for the splash when hitting the water implies a bellyflop landing, further complicating things.
Solar and Lunar: Waterbenders and Firebenders draw strength from the moon and sun, respectively; a Waterbender's strength is greater when the moon is up, and at its absolute greatest when the moon is full, while a Firebender's strength is greater while the sun is up. Additionally, Waterbenders and Firebenders lose their bending during their respective eclipses.
Solid Clouds: Lampshaded in the Water Bending Scroll. Katara mentions that she would love to walk on the clouds passing by. Aang tests this, concluding that "Clouds are made of water."
Sorting Algorithm of Evil: Zuko is the first antagonist, possessing a single ship and the crew therein in his quest to capture the Avatar. He is quickly surpassed by Zhao, a non-disgraced Commander (later Admiral) who eventually gets command of an entire naval fleet and provides the first real test of the Gaang's skills. When Azula and her Quirky Miniboss Squad come in the second season, the threat level spiked well beyond the Gaang's ability to handle at that point seeing the second season end with a major downer ending. And then Fire Lord Ozai got involved.
Spell My Name with an S: No confusion among fans as to how to spell names, but the official spellings often differs significantly from what you might expect based on the pronunciation. For example, Mai is in fact named for the Chinese word for beauty, which is "mei"; Ty Lee sounds like Tai Li, Joo Dee probably ought to be Zhu Di, and Iroh is pronounced like Airou would be.
Sphere of Power: Whenever Aang enters the Avatar State, he bends the air around him to create a bubble of high-speed wind. In the finale, he combines this with rings of water, earth, and fire.
Spirit Advisor: All previous Avatars become this to the current one. Roku is the one to whom Aang speaks the most often.
Spoiler Recap: Episodes will often open with a recap of anything from an earlier episode that is related to the current one in any way; if scenes from the episode "Jet" show up in the recap, don't be surprised about the character Jet suddenly showing up in the episode. The Order of the White Lotus was given obvious importance extremely early because of this, for one example.
Spoof Aesop: "The Waterbending Scroll". Katara steals and justifies it by saying that it isn't wrong as long as you steal it from pirates.
Spotlight-Stealing Squad: Katara during the season 1 finale. There's no logical reason for the North to be sexist, and that subplot afterwards disappears without a trace, suggesting it was only there to give Katara something to do, but it completely dominates the story, overshadowing Sokka and Aang's own plots. Though Aang does take back the reins when the Fire Nation shows up.
Squee: During the Beach Episode, when Zuko takes off his shirt and the camera cuts straight to nearby bikini girls enjoying the view.
The Foaming-mouth Guy from Kyoshi Island is prone to this whenever Aang shows up.
Stand-In Parents: Sokka and Katara stand in as "Kuzon"'s parents Wang and Sapphire Fire, when he gets into trouble at school.
Stating the Simple Solution: Ozai wonders why Zuko doesn't just kill him, seeing as Zuko has just cornered him during a solar eclipse (i.e. no firebending) and has a pair of swords pointed at him. Zuko states that that's the Avatar's destiny.
Zuko's right, in a sense, as reflected later during the finale, when the protagonists ask Iroh to defeat Ozai in Aang's place. His reasoning is that even if he could, history would only see it as a brother killing another brother for power. Similarly, if Zuko killed Ozai it might end the war but it wouldn't bring peace, especially given Ozai's vulnerable state. Only the Avatar, as the guardian of balance, really has the right to pass justice in this scenario.
Stay in the Kitchen: The Northern Water Tribe only trains men in combative waterbending; women can only learn healing techniques. It's implied that this may change after Pakku accepts Katara as his student.
Stealth Pun: The morning after Sokka is shown to be waiting for Suki in his tent wearing only his underwear, he is wearing a necklace of flowers. He got "lei'd", and Suki got "deflowered."
In "The Ember Island Players", the Gaang goes incognito to watch a play that recaps the story so far, and Sokka wants to meet the actor-Sokka, so how does he introduce himself? As "a big Sokka fan." Say it out loud a couple of times.
Stepford Smiler: Joo Dee has an extremely wide and fake-looking smile on her face at all times, even when she's warning the Gaang against stepping out of line. The smile only fades into tears once, and after Long Feng re-applies her brainwashing, it's back.
Stockholm Syndrome: We know this is at least somewhat the case regarding Zuko's desire to pleaseOzai. The question is: how much more abuse did he actually go through? And how much of that is also the case for Azula? Both are much more fragile and battered than anyone realizes...
Strong Family Resemblance: Both Sokka and Zuko strongly resemble their fathers (down to the designs for their fathers being based on the sons in question). It's lampshaded for both of them - Bato comments on the resemblance (down to similar senses of humor) between Sokka and his father in the second season, and Zuko points out that the smiling toddler from a scroll being joked about is actually Ozai and not him in the third season.
Stuff Blowing Up: A mountain full of methane pockets. And one of them is right underneath the Fire Nation invading force. Guess what happens.
Azula seems to think a volley ball-like game called Kuai Ball requires explosions.
Stunned Silence: Azula is trying to seduce a guy in "The Beach", but her megalomaniacal side kicked in, leaving him just, well, stunned into silence.
Aang's first real communication with Roku could only happen on the winter solstice, which was indicated by a beam of sunlight shining on the forehead of Roku's statue.
The door to the Sun Warrior temple would only open when the sun, focused through a lens, struck a stone on top of the door frame. Aang and Zuko were able to cheat by reflecting the focused light beam onto the stone, rather than waiting for the right time of day.
Superpowerful Genetics: Bending is partly genetic, though mostly random. See: Katara, the only bender in an otherwise non-bending family; Zuko and Azula, two powerful firebenders who come from a long and storied line of firebenders; and the twin brothers of "The Fortuneteller", one is an earthbender, the other isn't.
Supporting Leader: Uncle Iroh, when he leads the forces of the Order of the White Lotus to retake Ba Sing Se.
Surprise Witness: Subverted in the Trial episode. Avatar Kyoshi comes through Aang in a vain hope of proving the Avatar's innocence towards the murder of their king, although she ends up saying that she killed him for being a tyrant. However, after all was said and done...
Aang: What just happened? Katara: You kinda just...confessed.
"How do I land this—Ackk! Bug! BUG! That was a BUG!"
Sweet and Sour Grapes: Guru Pathik's admonition was incorrect, at least as Aang took it. Aang mastered the Avatar State by letting go of his love for Katara, but still loves her outside of the avatar state
And don't forget Momo vs. Appa in "Nightmares and Daydreams", where Appa quadruple wields katanas.
Sword over Head: After Zuko defeats his arch rival, Commander Zhao, in an Agni Kai (one-on-one firebender duel), Zhao expects Zuko to kill him with a Finishing Move, but to his surprise, Zuko spares him, blasting the ground near his head.
Symbolic Blood: In "The Guru", Katara is incapacitated by Ty Lee as she tries to get water out of her flask for bending. She ends up unconsious on the floor, with an expanding puddle of her bending water flows about her stomach, looking for all the world like a pool of blood.
Take a Third Option: Aang energybends Ozai to rob him of his firebending rather than kill him or be killed by him.
Also: Ozai could either kill Zuko, or give up his claim to the throne. Instead Ursa took a third option for him, assassinating Azulon and setting Ozai up as heir, then fleeing into exile.
In an early episode, Aang is presented with two armed men to duel against. He, instead, chooses King Bumi, the doddering old guy who's been testing him. Much to the audience's delight, Bumi reveals himself to be a Badass Grandpa...
Take That: "The Ember Island Players" is a gentle, good-natured "take that" at what the creators perceived as the more extreme parts of the Avatar fandom, including Fan Fic writers, Zuko-Katara shippers, and what happens to Jet. "Did Jet just... die?" "You know, it was really unclear."
Word of God says the absurdly violent armor Aang tries on in "Sokka's Master" was a jab at the makers of the action figures, who kept demanding Aang have some sort of "battle" outfit; as well as at Scary Impractical Armor as a whole.
Tanks for Nothing: Though the Fire Nation's mechanized forces give them a big advantage in the overall war, this is mostly played straight in the series, especially in the finale.
Averted (mostly) with the 'Caterpillar' tanks the heroes used on "The Day of Black Sun, Parts 1 & 2". Aside from cannon blasts from nearby battlements, ordinary soldier's firepower was simply insufficent to slow them down or damage at all (similar to Real Life tanks).
Sokka also performs this trope in the episode where he undergoes his training as a swordsman. Faced with a selection of metals with which to forge a sword, he picks up a hunk of the stuff and gnaws on it.
Team Dad: Zuko. Especially towards Aang and in the◊comics◊. He's also one of the only members of the team who doesn't get Katara's motherly treatment.
Team Mom: Katara. This is made blatant in "The Runaway", which explores how much the team depends on her, as well as the downsides of this trope. In the same episode, Sokka privately admits that Katara is almost more like a mother to him than a sister. And in turn, Toph admits that Katara cares about her more than Toph's real mom ever did.
Tear Jerker: "The Tale of Iroh" full stop. In-universe because we find out that Iroh's cheerful jaunt through Ba Sing Se dispensing wisdom and cheering up crying babies is actually his journey to observe the anniversary of the death of his only child. Out of universe because this was the first episode to air after the death of Mako, who was Iroh's voice actor. This tale is famously known for making fans of ATLA spontaneous burst into tears whenever the phrase "Little Soldier Boy" is mentioned....Oh God.
Technical Pacifist: Most of the good guys are this, considering it's a kid-friendly show, but the topic is actually brought up and discussed. While asking past avatars for guidance on how to stop Ozai without killing him, Kyoshi reminds Aang that she killed Chin the Conqueror to stop his invasion of her village. Aang points out to Kyoshi that "technically" she didn't kill Chin, he was just too stubborn to move away from a collapsing cliff side created by Kyoshi. Kyoshi claims she doesn't see a difference.
Blue fire signifies a higher firebending power, though so far only Azula had been demonstrated using it. This could actually be a case of Shown Their Work, because the hotter parts of a regular fire are, you guessed it, blue.
Long Feng's office has a fireplace with crystals burning with green flames.
Tell Me How You Fight: Not only is each kind of bending based on a visually distinct and appropriate martial arts style, but there are noticeable differences in how the various fighters execute those styles.
For example, while earthbending is mostly based off the Hung Gar style of Kung Fu, Toph's style utilizes several elements of Southern Praying Mantis style, particularly the precise steps which allow her feet to stay in contact with the ground so that she can "see".
Tempting Fate: Sokka is to blame for 70% of instances relating to this trope.
Near the end of book 2. The Gaang have convinced the Earth King there is a war outside Ba Sing Se, they have the entire Earth Kingdom on their side, they have info which would guarantee their victory against the Fire Nation, and Aang is going to be taught how to control the Avatar State. Sokka is far more positive and thinking along the lines of "Nothing can go wrong now." Then Azula, Ty Lee and Mai show up posing as the Kyoshi warriors and it's all blown to Hell.
In the second to last episode of Book 2, Yu and Xin Fu capture Toph, put her in a metal cage and declare that she may think herself strong but not even the greatest Earthbender in the world can bend metal. Guess what skill Toph created from scraps before and declaring herself the greatest Earthbender in the world...
Tentative Light: From the episode "The Cave of Two Lovers": Aang and Katara are separated from the others. They haven't found their way out of the cave and their torch is burning down to nothing. Turns out, the key to finding their way through the cave was to let their torches burn out, allowing them to see the dimly glowing crystals in the cave that marked the path.
Theme Naming: The three sets of siblings in the cast all share a syllable of their name: Sokka and Katara, Ozai and Iroh, and Zuko and Azula.
Even the tentative "Legend of Korra" falls in line with another existing line of Theme Naming: Kanna, Kya, and Katara, all Water Tribe women. Speaking of which, the only named Water Tribe members whose name didn't contain a "K" or a "A" were Yuenote She was named after the moon and Ummi (Kuruk's wife)note named after the ocean.
The Good, the Bad, and the Evil: Becomes this way at the end of season one, with the roles being filled by Team Avatar, Zuko and Iroh, and Zhao respectively. In season 2 and 3, Azula takes Zhao's place.
The "The" Title: Nearly all the episode titles take the form "The [noun]". The noun generally refers to either the primary setting, a character of the week, or a MacGuffin.
The Three Faces of Eve: The manipulative, charismatic leader Azula (seductress) and her two friends — sweet, affectionate Cloudcuckoolander Ty Lee (innocent) and calm, sane, level-headed Mai (wife).
This Is No Time for Knitting: Aang, Sokka, and Katara are fighting pirates on a ship about to go over the Inevitable Waterfall. Aang suddenly stops fighting and blows the "broken" whistle he bought earlier in the episode. Sokka screams, "Have you lost your mind? This is no time for flute practice!" before learning (along with the viewers) that it's a bison whistle Aang can now use to summon Appa to save them.
Thoughtcrime: Ba Sing Se had no idea that an incredibly destructive war went on outside of their walls, with inhabitants that think differently and make a fuss about it being brainwashed.
Thou Shalt Not Kill: Aang, although it was really an issue of premeditated, deliberate killing. In battle and self-defense, his fighting style generally lends itself to non-lethal subduing of his foes, so deaths, if they do occur, can at least be said to be unintended or accidental.
After Appa is stolen, Aang is enraged when a vulture wasp tries to carry off Momo. Even after freeing Momo, Aang proceeds to obliterate the wasp with a powerful airbending strike (which, by the way, is a bending form confirmed to be completely lacking in lethal moves). It's Aang's only confirmed kill in the series.
Iroh took yet another level in it to prepare for his prison break.
Tornado Move: Aang sometimes does this, using it to directly assault opponents, levitate himself or shoot rocks as if from a cannon.
Total Eclipse of the Plot: Used by the group to attack the Fire Nation. Justified, since firebenders gain their power from the sun — an eclipse leaves them powerless. And realistically, it only lasts eight minutes.
Training The Gift Of Magic: One is apparently born as either a "bender" or "non-bender". Without training, Katara's "waterbending" is little more than a parlor trick; you could move more water just by splashing with your hands. With training, she is capable of manipulating, freezing, and thawing large quantities, and even (under the right circumstances) manipulating water in people's blood to make People Puppets out of her enemies. It does appear to be possible for some prodigies (such as Avatar Korra of Avatar The Legend Of Korra, who is seen bending three of the four elements at a very young age with little or no formal training) to be self-taught, but it is very rare.
Training Montage: In "Sokka's Master", which is, in essence, one episode-long Training Montage
Truth in Television: Many survivors of abusive families can confirm that, paradoxically, the "favorite" of an Abusive Parent often becomes the one most screwed up by said parent — because it's that much harder for them to cut ties, leaving them stuck with the parent even after all the other siblings have escaped. This is exactly what happens with Azula and Zuko. Zuko is The Unfavorite who gets mutilated and thrown out, but that lets him out of Ozai's influence long enough to gain Character Development, have a Heel-Face Turn, and ultimately move on to a new life after the war's end. Azula, meanwhile, is trained by her father into a total psychopath and stakes her self-worth on his approval to the extent that it ultimately breaks her. By series end, she's in a mental hospital.
Mai: Orange is such an awful color. Zuko: You're so beautiful when you hate the world. Mai: I don't hate you. Zuko:I don't-hate you, too.
TV Teen: Both played straight (everyone's skin is perfect, and some of the VAs are well past 30) and subverted.
24-Hour Armor: Averted with most of the main characters, who only wear their combat attire when in they're actually going into a major battle, particularly during the invasion of the Fire Nation in season 3. Played straight, however, with a lot of B characters, though justified in that many of them are soldiers and must always be on alert.
Twist Ending: Prominent throughout Season 2, in contrast to the usual "ride off happily into the sunset" endings of most episodes in Season 1. One episode in which it was played with contained several plot twists at the end.
Uncertain Doom: The show is deliberately vague about whether or not Jet died. The final fates of some other characters are similarly never revealed.
Underside Ride: This is how Zuko gets inside Zhao's compound, during "The Blue Spirit" episode, by hiding beneath a layer of dirt in the road. Then grabbing the undercarriage of a supply wagon as it passes over him. It takes him straight inside the fortress.
Unfamiliar Ceiling: Aang waking up at the beginning of Season 3, six weeks after being struck by lightning.
The Unfavorite: Zuko to Ozai. Azula to Ursa, though probably with more pity than malice. And also Ozai to Azulon.
Uniformity Exception: In the first Northern Water Tribe war episode, Zuko disguises himself as one of Zhao's Faceless Goons. Zuko's eyes are visible through the mask's eyepiece, whereas the other goons have their eyes concealed.
Momo hearing people and understanding them is situational by Rule of Funny. There's at least one occasion where Aang tells Appa and Momo to stay out of sight. Momo immediately finds a hiding place; Appa tries the same hiding place, but since it's a bush, it does not work so well.
Unwitting Pawn: If Zuko's word is to be considered, it would appear that this is the case with the majority of the Fire Nation in regards to the war, and that only the most cold-hearted and sadistic people are given the truth. It is worth noting that Fire Lord Ozai is careful to keep these people close to him, perhaps not wanting word to get out.
Zuko: Growing up, we were taught that the Fire Nation was the greatest Nation in history; and that somehow, the war was our way of sharing our greatness with the rest of the world. What an amazing lie that was. The people of the world are terrified by the Fire Nation! They don't see our greatness; they hate us! And we deserve it.
Useful Notes on China: "Laogai" is actually a phrase referring to reformative training, usually associated with Communist China.
The background music in Earth Kingdom dinner scenes ('The Blind Bandit' and 'City of Walls and Secrets') is an actual traditional Chinese tune called 'Mo Li Hua' or Jasmine Flower.
From the end of "Avatar Day": fried dough sticks to represent hated historical figures do exist.note You can see the Landlord bumming some off of Donut early in Kung Fu Hustle. Long story short, Evil Chancellor Qin Hui set up the Emperor's most loyal general Yue Fei as a traitor, leading to his execution before the truth was out. The fried dough sticks are always made in pairs to represent Qin and his wife.
Energybending in the Grand Finale becomes less of an Ass Pull if you're familiar with Chinese martial arts fiction, which commonly used "the removal of his martial arts" (via crippling nonfatal injury) as a Fate Worse than Death for villains. Another common trope from this genre is having your villain driven insane with his own growing abilities... which might explain Azula (or Bumi, but he was always a little odd).
In a similar vein, Metalbending. Toph is shown using two different martial arts styles for standard (Hung Gar) and her self-developed (Mantis) Earthbending; Metalbending comes from a third style, Xing Yi Quan, developed in captivity just like Toph's metalbending was. note Jet Li uses this style in The One, when he bashes the prison walls just like Toph does, while his good counterpart uses a different style, Eight Trigrams Palm, same as Aang).
And bloodbending is based on Qin Na Shou, an appropriately grapple-based technique.
The statue and idols that the villagers were fond of also appeared to have a bare back.
Variant Chess: Pai-sho. Has a black and white board like chess, a star shaped playing field like Chinese Checkers, and large checkers with symbols, indicating the type of piece is represents. Its rules are never seen.
The board starts out empty, and players take turns placing pieces on it, much like Go, but unlike Go, the pieces are not all the same and presumably different ones do different things (like in chess), but unlike chess, the pieces are tiles, not statuette figures. So it's essentially Variant Chess Go Mahjong.
Very Loosely Based on a True Story: Inverted. The Ember Island Players version of the Gaangs journey; in most respects they've Shown Their Work. They pretty much do the Abridged version of every episode up to that point (which, as it happens, was the last before the finale`); the only thing that really sticks out is cast and characterization, and even then the Gaang mostly just disagree, or dislike, on how they themselves are portrayed (like Aang being played by a woman, or Zuko being reminded of his treachery- Toph and Sokka love their portrayals, though). The only difference is how it ends (The Bad Guy Wins- its a Fire Nation play, after all), and even then it's technically correct - Zuko does fight Azula and Ozai does take on Aang, and in a sense both villains do beat the crap out of the heroes - the good guys just end up ultimately turning the tables.
Victimized Bystander: It's a Running Gag that the Gang will somehow cause his cabbage cart to get destroyed and he'll scream "MY CABBAGES!".
Victorious Childhood Friend: Aang, in a sense. He and Katara haven't known each other from childhood, but he was plagued with all the psychological baggage that comes with this trope for the entire series. Also, in a more traditional example, Mai.
Villain Protagonist: In-universe example. The Gaang goes to see a play about themselves in "The Ember Island Players". The play was written by a Fire Nation playwright and written for a Fire Nation audience. The Gaang's exploits are played (somewhat) villainously, most notably Actor!Katara's reaction to Actor!Jet destroying the village. And the audience cheers when Actor!Azula "kills" Actor Zuko, Actor Ozai kills Actor Aang and when the Actor!Gaang is defeated.
Villainous Valour: The commandant of the Boiling Rock is a brutal authoritarian and a thug. He is also perfectly willing to command his own men to kill him rather than allow enemies of the Fire Nation to escape his prison.
Villains Out Shopping: The episode "The Beach", which as its name suggests, involves Azula and co. hanging out at the beach.
Violently Protective Girlfriend: Let's just say that potential harm to Aang is a very bad idea. Zuko received a death threat over it and Hamma became the victim of Katara's first use of blood bending when she tried to kill him in "The Puppetmaster".
When Azula attempts to murder Zuko, Mei opts to betray her friend and attack her fellow countrymen rather than let her boyfriend fall to his death.
War Is Hell: A kid-friendly version of this trope appears in most episodes, and the show seriously explores the prolonged effects of Imperialism, foreign occupation, and even genocide while still remaining viewable for the whole family. It's responsible, yet brutal depiction of war and its consequences was one of the stated reasons for why it won a Peabody Award.
"Little soldier boys, come marching home...."
Warrior Prince: Prince Zuko, even Iroh, technically, since he still holds the 'prince' title, although he tends to go by 'General' now.
Watch Out for That Tree!: Aang does this in the opening credits, as well as Sokka's snow tower in the pilot and a pillar in the second season premire.
Watching the Sunset: Usually done at the end of certain episodes. It's also the last scene in the series.
Wearing a Flag on Your Head: An in-universe example. All the citizens of any of the four nations wear their nation's colors, and most will have their country's emblem somewhere on their clothes. All the time. To the point that, while hiding out in a non-native kingdom, virtually the only thing any of the characters must do to blend in is wear that nation's colors. Overlaps with the Color-Coded for Your Convenience of the show.
We Will Meet Again: In Season 1, Zuko says it to Iroh to reassure his uncle that Zuko will survive his plan to take the Avatar at the North Pole.
Also said by Koh to Aang in the same two-parter. They don't in the shows, but Aang meets Koh again in a supplemental game on the Nickelodeon website.
"Well Done, Son" Guy: Zuko's been away from home for three years on a mission to "restore" his honor and prove to his father that he's worthy of the crown. At least, that's what he tells himself. He finds out later that he just wanted his father to accept him for who he was; it took him two and a half seasons to realize that it would never happen. This also applies to Sokka. Luckily, his dad explicitly tells him that he doesn't need to prove himself, because he's already proud of him.
Wet Means Defeated: Seeing that this show is aimed at a younger audience, and that there are people who can bend water, plenty of bad guys end up like this, though mostly those of the Fire Nation Mook category.
Wham Line: Zuko is the recipient of one in "The Avatar and the Fire Lord"; after being told by Iroh to look at the story of how his great-grandfather died, he looks up Sozin's personal history, only to learn nothing he doesn't already know. When he hears it, he has the facial expression of someone who soiled themselves:
Iroh:(to Zuko) You have more than one great-grandfather, Prince Zuko. Sozin was your father's grandfather; your mother's grandfather was Avatar Roku."
Toward the end of the first season, it appears the Waterbenders will gain the advantage at night.
Zhao: (to Iroh) I assure you, I have everything under control. I intend to remove the moon as a factor.
From "Lake Laogai", we get this wham line from Toph, regarding Jet, as he's dying as assuring his friends that he'll be OK:
Toph: He's lying.
From The Puppetmaster:
Hama: Congratulations Katera, You're a blood-bender
What were the details of Iroh's legendary "journey to the spirit world"?
Word of God says that Iroh's journey to the spirit world was an attempt to find his dead son
Did Toph have a reunion with her parents and what was it like?
The Rift comic has her meet her father.
What happened to Ursa?
This isn't revealed in the actual show, but it's the focus of The Search.
What happened to Hawky?
What happened to the flower necklace Aang made for Katara in The Fortuneteller?
Written off as an animation goof
Shyu, the only fire sage to still be loyal to the Avatar, and in reality the Gaang's first fire nation ally. He helped them get past his fellow sages and talk to Roku, disappeared during the destruction of the Fire Temple.
What happened to the other fire sages?
They were all accused of treachery by Zhao and taken to the Fire Lord at the end of the episode so they might have just been killed.
What happened to Chit Sang, the prisoner that escaped with Sokka, Zuko, Hakoda, and Suki from the Boiling Rock? We see him, Hakoda, The Duke, Teo, and Haru escape on the stolen airship in the beginning of "The Southern Raiders." Everyone except Chit Sang appears at the end of the finale.
Sokka calls out Jet twice over his extreme behavior, such as robbing an old man simply for being a Fire Nation citizen and later for trying to drown an entire town full of people to get at a few Fire Nation soldiers. This also earns reprimand from Aang and Katara, who were tricked into helping. Also done to Aang in regards to his 100-year absence early in the series - though in his case, he already felt guilty about it.
Wan Shi Tong, guardian of the spiritual library, is immensely fed up with people who come seeking knowledge of battle and warfare under the excuse that this war is perfectly justified and righteous, and he lets the heroes know it. Further justified in that, while Aang and friends weren't responsible for it, the current war did result in a good chunk of the library getting damaged.
Jet gets another one when, instead of going straight, he decides to find evidence of Iroh and Zuko being Firebenders, so that he can turn them in.
Katara gets her own when she tries to take Appa behind the group's back for her selfish quest of personal vengeance. During which she tells Aang, who lost his entire civilization to genocide, that he doesn't understand her pain, while telling Sokka he must no have loved their mother enough.
What Would X Do?: "What would Uncle do?" is a question Zuko frequently asks himself when trying to do the right thing in Season 3. Sometimes results in Ice Cream Koans.
Aang does this just before consulting the previous avatars for advice.
Whip It Good: A frequently used waterbending technique. Firebending, as well: Zuko in the second finale against Katara's water ones, along with a stage magician and a circus animal trainer.
White Man's Burden: This is the Fire Nation's official reason for conquering and colonizing the rest of the world: they want to "share their greatness" with the rest of the world. Certainly, Azulon and Ozai don't care about that and they just want to be the supreme ruler of everything, but that was Fire Lord Sozin's reason for beginning the war in the first place.
Season 1's "The Deserter" shares too many plot elements with Apocalypse Now for it to be coincidence. Jeong Jeong is a Colonel Kurtz expy, and Chey (voiced bythe Crypt Keeper, of all people) bears an equally strong resemblance to Dennis Hopper's unnamed photojournalist character.
Why Did It Have to Be Snakes?: Toph, due to her Disability Superpower, really dislikes flying, sailing, or riding huge mounts, though not to the extent that she's outright scared (Then again, she does mention that riding Appa without a saddle is terrifying). Appa, being a Sky Bison, hates going underground, and also develops a fear of fire following the events of "Appa's Lost Days"
William Telling: In a flashback to Zuko's childhood, Azula put an apple on Mai's head and hit it with a fire blast, telling Zuko it was a "game". Mai freaked out from having a burning apple on her head and Zuko, trying to help her, accidentally knocked her into the fountain. All this because Azula suspected Mai had a crush on Zuko.
Window Pain: In "Tales of Ba Sing Se", Iroh encounters a group of children who put their toy through a window. But instead of glass, since the setting hasn't got that yet, the window is rice paper. They get the same Broken Glass Penalty anyway.
In the first episode, Aang tells some guards that he could take them with his hands behind his back (which, he proceeds to actually do). King Bumi also manages to show his skill while trapped in a solid metal box.
Aang explicitly asks how Bumi is able to earthbend while in said box, with his body locked in place. Bumi's response: "They didn't cover up my face!"
He does the same trick twice, breaking out of the box using only his face during the Day of Black Sun and proceeding to take Omashu back on his own.
That example was exceptionally skilled earthbending also because they tend to need some contact with the earth in order to bend (although Toph can bend earth which in the air). Bumi's metal box is suspended high above any earth, and with his face alone he draws enough earth to him to break out. Aang uses a similar distance trick for his Sphere of Power in Sozin's Comet.
Iroh does this when captured by earthbenders, only he actually uses the shackles to aid in his delivering a beatdown. Twice in one episode.
As the Avatar Extras put it, "Earthbenders 0, Naked Shackled Guy 3."
Subverted when the group is captured in the Earth King's throne room in "The Earth King". Aang pulls his hands free to wave and puts them right back, despite his earthbending being at elementary level.
Earlier in the episode "Avatar Day", Sokka summed up the whole experience, "This is by far the worst town we've ever been to."
Would Not Shoot a Civilian: The Gaang and even Sokka, for all his hating of the Fire Nation, holds to this trope. In "Jet" when Jet's idea of fighting the occupying Fire Nation is to blow a dam to flood a village of civilians with some soldiers the Gaang tries their best to stop it.
Fire Lord Sozin was 82 when Azulon was born, Azulon was also likely between his 50s and 60s when Ozai was born. Justified in that while this is strange, even in Real Life men, unlike women, can produce offspring.
Fire Sage Shyu is about 60 during the present, and his grandfather was already an old man when Roku was in his 20s! Possibly justified in that people have been shown to be incredibly long-lived in the Avatarverse.
Koh mentioned that Avatar Kuruk tried to slay him 800-900 years before Aang came to see him, long before Kuruk could've possibly be born according to the timeline.
Wrong Context Magic: When it comes to bending, the Avatar goes by different rules than anyone else; Aang can bend all four elements, access the Avatar State, and use other spiritual powers. Sokka eventually lampshades how spiritual abilities don't fit with how the rest of the world works by saying "That's Avatar stuff; it doesn't count."
Xanatos Gambit: Azula giving Zuko the credit for killing Aang in the Season 2 finale. If her victim survived then she's in the clear and in the meantime she has blackmail on Zuko.
You Know I'm Blind Right?: Toph's friends (especially Sokka) have a tendency to forget that she's blind. Her best example of Lampshading was when Katara showed her a wanted poster, when Sokka had done the same thing earlier in the episode:
Toph: "I don't know! I mean seriously, what's with you people? I'm blind!"
You Need to Get Laid: Iroh to Zuko. "I just want our new place to look nice, in case someone brings home a lady friend..."
Also, Katara to Sokka. "I bet you wouldn't be so bossy if you kissed a girl."
Your Costume Needs Work: Aang tries to get his group free passage on the ferry to Ba Sing Se, and the woman taking tickets doesn't find his Avatar costume any more believable than those in the nearby group of Aang cosplayers/impersonators.
In "Ember Island Players", a kid tells Zuko that he got his scar on the wrong side.
Zeppelins from Another World: The single biggest Oh Crap moment in the series after Azula ambushing Aang with her lightningbending. Granted, there had been foreshadowing at the end of the episode introducing the war balloon, with the Fire Nation officer finding it after the battle. So they showed a fleet of war balloons for the initial Oh Crap, and THEN came the zeppelin armada.