"I have decided to record everything I know about Subject. To know your enemy is to have a great advantage on the battle field. I have decided not to name Subject for confidentiality's sake as well as because calling things by their name eventually endears them to you. Subject will not endear himself to me again!"
A Birthday, Not a Break: The events of "The Southern Raiders" happened around Katara's birthday, and since it was shortly after the anniversary of her mother's death, her mother's death also fell close to that birthday. To make matters worse, she's also separated from her father as a result of Azula's attack.
All Love Is Unrequited: Played with. Katara and Zuko do have feelings for each other, but are afraid to admit it. Played straight with Mai and Jet, who have feelings for Zuko, and Aang, who has feelings for Katara.
All There in the Manual: Some details that Katara misses are pointed out by the author. For example, it's revealed that Zuko was considering quitting fire flakes for Katara's sake, until she surprised him with a gift.
Abandoned Area: There are a lot of abandoned soldier homes all over the Fire Nation. After "The Southern Raiders", the Gaang hides at one before going to Ember Island.
Adaptation Expansion: The fanfic expands on what happens between episodes, in part to allow for more interaction between Zuko and Katara.
Bedlam House: Averted. When Azula is institutionalized, they treat her very gently and hope for her recovery.
The Beautiful Elite: The Water Tribes apparently seem to be this to Fire Nation girls. Mai jokes that the Water Tribes banish the ugly children at birth. A strange example, as the Water Tribes are stereotypically barbaric in comparison to the Fire Nation.
Better Than Sex: Suki declares the dragonberries to be this, which greatly worries Sokka.
Betty and Veronica Switch: Mai is the Betty and Katara is the Veronica with their traits switched around. Mai is Zuko's childhood friend, the "safe" choice, and a lady of the court, but with Veronica traits like being different from what he's used to (after his banishment and traveling), is very wealthy, used to commanding servants, and is an Ice Queen. Katara is the Veronica in that she's exotic, seemingly unattainable due to their past history and possible futures, is outside of his world (the Fire Nation), and seemingly unaware of Zuko's affections. However, Katara has Betty traits such as being emotionally reliable, Zuko's best friend, and part of Zuko's past lifestyle of banishment, chasing the Avatar, traveling, and re-banishment.
Big Fancy House: Zuko's vacation home on Ember Island. In fact, he used this trope to convince the Gaang to hide there. The royal villas are also this, seeing how they used to house the royal family.
Blazing Inferno Hellfire Sauce: Fireflakes are very spicy to non-Fire Nation people. Averted with Fire Nation colony cuisine, which has evolved to use less spices due to the difficulties bringing them from the homeland and absorbed elements of Earth Kingdom cuisine.
Book Burning: Firelord Sozin kept many original documents and scrolls that he raided from invaded areas and burned everyone else's copies. Also, Zhao's burning of the Fire Nation section of the Wa Shi Tong's library, while practical, is seen as very unusual.
Boring, but Practical: In a Continuity Nod and Call Back, Zuko's firebending lessons to Aang. Aang finds Zuko's lesson extremely boring and dull, but Zuko points out how dangerous fire is, so it's more important to know how to block before learning how to attack.
Chekhov's Gun: Zuko's protectiveness of his uncle in Jet's Troubling Obsession and how Iroh is able to make so much tea. Jet decides that Zuko's not a firebender, but Iroh is. Zuko's attack on Jet when he deduced this proved his point.
Conscription: The Fire Nation has this, with the rich draft-dodging and most of the recruits being from the lower classes.
Cry into Chest: Zuko ends up comforting Katara this way after the Southern Raiders, although he was very awkward about it at first.
Cultured Badass: Suki, Toph, and Zuko can play musical instruments due to their backgrounds.
Cucumber Facial: The spa day that Toph gave to Katara for her birthday had this.
Damned by Faint Praise: The best thing Teo can say about sea prunes are that they aren't the worst thing he's eaten. Considering that he's eaten grass as a refugee, that isn't saying much.
Water Tribe patriarchy astounds Zuko and Katara (thanks to her basically growing up with no men around to enforce it), and the Fire Nation judges mental illness with Victorian-esque values which matters when Azula gets institutionalized after her Villainous Breakdown.
The author points out that the Water Tribe has virtually no concept of privacy. Sokka found Katara's diary while looking for seal jerky, and only (reluctantly) kept quiet out of love and respect for Katara and Suki, as well as fear of what they'd do to him if they found out.
Environmental Symbolism: Katara thinks the rain was in sync with her crying, it stops raining and a rainbow comes out after she lets it all out.
Elephant in the Living Room: the Gaang try to leave Aang ignorant of the consequences of the Siege of the North. Shot down when Arnook gleefully tells Aang of all he had killed by drowning.
Equal-Opportunity Evil: Discussed to why this happened to the Fire Nation: due the extensive war effort more women entered the workforce. Women started to be paid and treated equally after they striked for equal pay, bringing the economy to halt until the people in charge gave into their demands.
Exact Eavesdropping: Downplayed. In Not Stalking Zuko, Katara happens on Zuko and Aang just as they start talking about Aang's desire to help Katara accept Air Nomad culture, but midway through, Zuko vaguely references something he said while Katara wasn't listening in on them.
Exiled to the Couch: In the first part of Not Stalking Zuko, Zuko is often sexiled to the couch by Sokka and Suki.
He Is All Grown Up: A platonic version between Fat and Zuko, who last saw each other when Zuko was a child.
Henpecked Boyfriend: Sokka is seen for Suki as this by the Southern Water Tribe warriors, which actually makes Sokka feel uncomfortable as he feels that they are disrespecting both himself and Suki.
Heroes Prefer Swords: Lampshaded by Katara, when Sokka and Zuko teach The Duke swordsmanship with tree branches.
Hero with Bad Publicity: Aang has this with the Fire Nation. It's a Justified Trope; many Fire Nation citizens had relatives that were killed in the Siege of the North when Aang was in the Avatar State.
Hidden Depths: Everyone gets this but props has to go to one-scene characters Ming and Sorrak
Hotter and Sexier: A Boy In The Iceberg's late night show happens to very racy and sexy.
Hypocritical Humor: Katara tries to warn Zuko of him possibly getting stalkers after seeing his Groupie Brigade. Zuko rightly laughs at the irony of Katara warning him.
Katara meant this literally with Suki, when trying to explain worrying that a friend is not being careful with her lover. Suki answers her until Katara reveals she thinks her friend might be pregnant. Suki is at first disappointed when she thinks Katara was careless and understandably freaks thinking Katara got herself pregnant.
Hakoda tried to invoke this trope on Zuko to tell him the possible consequences of hooking up with Katara. It doesn't work because Zuko takes him literally.
In Vino Veritas: Zuko is affectionate and reckless drunk. Sokka is philosophical drunk. Katara gets extremely playful and flirty when Zuko tries to put her to bed. Mai is a shameless drunk.
Insane Troll Logic: Sokka says that since Katara spent three days alone with Zuko looking for the Southern Raiders, she must have had sex with Zuko. Katara turns it on him, however. She says by that logic she should assume Sokka had kinky prison sex with Zuko since he was alone with Zuko for five days.
Like Brother and Sister: In an Inverse from their the The Friends Who Never Hang in canon, Toph and Zuko are the closest to each other in the Gaang due to the many things they have in common: both were new additions to the Gaang and had to deal with the refitting of the group dynamic. Both came from lives of prestige and restriction and the fact they had to fight to get what they want.
In epilogue, Toph ends up living with Zuko and Iroh after the war
Logical Weakness: Why did no other firebender prisoner besides Zuko bend heat to keep themselves warm in the cooler? The answer: get cooler fever and now you can't defend yourselves from the guards or other prisoners.
Love Hurts: Zuko confesses as much to Aang in Not Stalking Zuko.
Luke, I Am Your Father: Played with and mocked. When Zuko revealed that Avatar Roku was his maternal great-grandfather, Aang realized that would make him Zuko's great-grandfather. Then Aang proceeds in asking his "grandson" for hugs.* Maid: The OCs found in the Fire Nation palace dungeon after the Agni Kai.
The Medic: As canon Katara but also the OC, Dr. Yang.
Men Can't Keep House: When the Gaang goes out to buy cleaning supplies for the vacation house they're squatting in on Ember Island, Zuko says they don't need to do so, prompting Katara to remark "Boys" in her narration.
Mistaken For Bi: Jet's stalking is mistaken constantly as having an unhealthy crush on Zuko. Jet's friends and therapist tell him that they're okay with his sexuality, just let go of Lee's "rejection" and move on to keep it from taking over his life.
Mistaken for Pregnant: Zuko and Katara feared Suki was this after Sokka told them of dreaming that they were penguins and a Penguin!Suki giving him a bag to lay on. Zuko feared this was a prophetic dream since they have been having sex a lot and Zuko didn't know whether they used protection.
Moment Killer: Frequently Sokka, but all of the Gaang get a chance to kill a moment.
Never Say That Again: During and after the Southern Raiders, Katara bans Aang from saying the "f-word." It's forgiveness, since while she doesn't have it in herself to kill Yon Rha, she can't forgive him, either.
Nice Job Breaking It, Hero: Aang doesn't kill Ozai and fulfills his Air Nomad beliefs...Now he completely destabilizes Zuko's legitimacy as Fire Lord and causes a Succession Crisis that nearly tears apart the Fire Nation. Since he establishes that he cares more about his own beliefs than the fate of the world as a result no one trusts him to actually take responsibility and fulfill his duty as Avatar.
The Nicknamer: KATARA. Subject for Zuko. Dippy-Flippy for Ty Lee. Gloomy Hairbuns for Mai. Chit Sang is also this. Azula, too.
The Not Secret: More people are aware of Katara stalking Zuko than she initially realizes. Zuko himself has known since very early on, much to Katara's dismay.
Not So Different: Suki and Zuko after their stealth-off realize that they are both really great at being "stealthy badasses" and both felt like outsiders to the group. Zuko also shares the latter with Toph, as well as their being from privileged backgrounds and having a bad relationship with their parents.
Offered the Crown: Zuko didn't believe that Iroh would actually make him Fire Lord, so he's genuinely shocked that Iroh wants him to take the crown.
Overshadowed by Awesome: Suki feels like this because she's not a leader like Sokka nor is she a bender like everyone else.
Padding: In-Universe, the writers of The Boy in the Iceberg don't know what the Gaang nor Azula, Zuko and their friends were doing after Ba Sing Se and the Day of Black Sun so they fill it up with wacky side plots and musical numbers.
Parents as People: Toph's parents wants what's best for her, but clearly don't understand their daughter and hurt her because of it.
The reason Mai's dad quits his job as ambassador of Omashu because he realizes that he missed the entirety of Mai's childhood and neglected her because of it. Mai's mother is a social climber and forced Mai to be prim and proper due to growing up in the Deadly Decadent Court of Fire Lord Azulon and is trying to ensure their survival under Ozai.
Quickly Demoted Woman: In-Universe, the Southern Water Tribe Warriors praise Sokka and Aang's accomplishments, but never acknowledge Katara, Suki or Toph's accomplishments. Then they expect Katara to do the sewing and cooking even though the villa has servants. This is used to show how sexist the Water Tribe men are.
Race Fetish: Ty Lee and other Fire Nation women have ones for Water Tribe men.
The Rant: The author's notes offers insight to the writing process, why characters act within fic, why certain cultural influences pop up and show the author's various questions regarding canon.
Red Baron: The Fire Nation's nickname for Hakoda is "the Blue Wolf".
Real Dreams Are Weirder: Sokka gets dreams of being a penguin and laying on a bag of fireflakes given to him by penguin Suki. Katara gets dreams of Master Pakku in Ba Sing Se showgirl outfit.
Real Women Never Wear Dresses: Subverted, for the author, being feminine doesn't mean anti-feminist. What's bad is when someone is shoe-horned into a role just because of their gender.
Deconstructed, in that Katara was willing to learn healing but didn't want to because she was not allowed to be anything beyond healer. She learns healing of her own accord and because she needs to, and then decides to train to become a doctor now that her warrior-bender skills won't be needed any more (she hopes).
In the Ember Island play, Stage Katara and Stage Zuko
Ty Lee is a somewhat more PG-rated version; the author's notes even say that one possible way that Aang might get her to accept that she's an Air Nomad by blood and is likely an unrealised airbender is by getting her to think that following Air Nomad philosophy — in particular the part about "Free Love" — will allow her the perfect excuse to sleep with every guy she wants without ever committing to any one boy in particular.
Reality Ensues: When Zuko is hit by lighting, he had to see a real doctor and was comatose for a few days and bedridden for a week afterwards. The whole fic has reality ensuing.
Twice more in Jet's Troubling Obsession, when Zuko tries to show Jin the view of Ba Sing Se, she lacks the fitness and strength that most of the Avatar cast has and had to be assisted by Zuko to get on the roof. This was supposed to compare the cast to normal people.
Jet's therapy proves counterproductive because he doesn't believe he has a problem.
Reality Is Unrealistic: Noted by the author when she did the research but had to go with the tropes because the actual treatments would have been too modern for the Avatar verse
Reign of Terror: Ozai had one, which is why most of the Fire Nation accept Zuko. Everybody with their head screwed on right figures he simply can not be as bad as his father was. The only ones to actively seek to enthrone one of the others are either direct profiteers from Ozai's reign or convinced they can "work around" Azula's psychosis.
Right for the Wrong Reasons: The Running Gag of Jet's Troubling Obsession, which ends up being Played for Drama in the final chapter when Jet realizes that while he never found proof for Zuko being a firebender, he saw many instances where Iroh was firebending. He realizes that Iroh was able to stay warm in their poor insulated apartment naked in early spring and is making large quantities of tea without firewood.
In a Played for Laughs version, Smellerbee. She thinks that Jet's obsession with Zuko is an unhealthy crush and Jet is afraid of coming out of the closet. So she and Longshot try to show their support of him, showing that they won't reject him for being bisexual and try to find Jet some help.
Royally Screwed Up: The Fire Nation has a long history of them, besides Ozai and Azula, there was a Fire Lady who only spoke to pineapples and required all of her courtiers to carry a pineapple so she could address the pineapple when she wanted to speak to the courtier.
Rule of Symbolism: Zuko's Fire Lord robes are too heavy and uncomfortable and Azula's pink hospital gown makes her look like a child
Secret Diary: Katara's stalker log. Naturally Sokka ends up reading it.
Secret Police: Besides the Dai Li, Ozai had one as well, which was responsible for causing many dissenters and noblemen to disappear.
Sex Equals Love: Discussed by Suki in Not Stalking Zuko. She says that because sex is something people who are in relationships often do, they "were all bound up together and sometimes confused with each other".
The author believes that Katara's feelings for Aang are maternal. Various incidents, such as Katara (and the author) believing that Aang does not understand her desire for revenge, and Katara's reaction to Aang sparing Ozai, help sink the ship.
Maiko is sunk by Azula revealing that Mai was her spy
The Shrink: Dr. Wang is type 3, but ends up being type 2 to Jet. Dr. Wang is able to pinpoint what Jet's problem is but Jet doesn't want to believe it.
Shown Their Work/Word of God: Every chapter ends with a long, rambly author's note explaining her thoughts on the subjects covered in the chapter and her interpretation of the related canon information.
Sliding Scale of Plot Versus Characters: Mainly on the characters side. The plot is largely driven by Katara and Zuko's relationship, and a good portion of what plot there is comes from the canon series.
Slut Shaming: Jet does this extensively to Jin, he constantly calls Jin a shameless hussy for daring to flirt with Zuko. Although this is emphasize Jet's irrationality and jealousy of her
Stalker Without A Crush: Katara was initially this to Zuko, to keep a lookout for his betrayal. Jet claims he's this to Zuko, and gives every sign of consciously believing his own hype (subconsciously, though, is another matter).
Stay in the Kitchen: Katara gets hit with this trope hard after Sozin's Comet when she reunites with the Southern Water Tribe Warriors. They don't even acknowledge her successes and immediately try to make her do the sewing and washing because she's there.
Team Chef: Lampshaded by Katara, she is only one in their group that can cook.
Therapy Backfire: Zuko and Smellerbee try to get Jet into therapy to for his obsession. Doctor Wang pushes Jet into a revelation, but not one they want.
There Are No Therapists: Averted twice with Azula who gets medical help and psychiatric from Dr. Yang, and Jet who is forced by Smellerbee into therapy with Dr. Wang.
There are no true therapists in the Fire Nation, in the Earth Kingdom however...
Thou Shall Not Kill: Deconstructed in that Aang's decision to spare Ozai's life and take away his bending goes against everyone's (including the past Avatar's) advice, infuriates everyone, and causes dire problems for Zuko's legitimacy as Fire Lord, which is seriously destabilizing the Fire Nation.
Through His Stomach: Hakoda and Sokka believe in this trope when Katara gives Zuko food, and Katara insists they're reading too much into it ("They are just fireflakes not a proposal of marriage"). Suki tries this with Sokka but turns out to be a Lethal Chef due to lack of experience.
Throw the Dog a Bone: Iroh giving Katara the respect she deserves by calling her Master Katara and acknowledging what she has done for the war after getting belittled by her own tribe. Also, Iroh stealing Piando's gift to Sokka to not shaft Sokka for not being a bender.
Torture Cellar: Ozai has one, and it is used as proof as why he shouldn't be Fire Lord — as much for the illegality of it as for the obvious signs of psychosis.
Traveling at the Speed of Plot: Lampshaded in-universe and in the Author's notes. To get the Fire Nation from the Earth Kingdom, Zuko and Katara had to take a shortcut through an ocean instead of their regular route which would take days.
Trilogy Creep: The series has expanded greatly over time, not just having the three main entries, but also having many side stories about other characters.
Tsundere: Katara is Type A, as Zuko was formerly their enemy and Katara doesn't trust him to not betray them, combined with Zuko constantly getting on her nerves for one reason or another. Katara is initially very hostile to Zuko until they become friends and Katara realizes her feelings for him. Then she is no longer this trope when she is crushing on him. Slightly deconstructed when Zuko gets worn out by her hostility and believes them not to be friends
Deconstructed with Jet; he is in denial about his feelings for Zuko, as he refuses to accept he's bisexual, and justifies his stalking as trying to out him as a firebender as opposed to rather creepy lust spawned by Zuko's rejection of him. Zuko, Smellerbee and Longshot believe him to have serious problems, it prevents Jet from moving on or helping his friends, and ultimately ends with the canonical events that lead to Jet getting arrested and brainwashed by the Dai Li.
Violently Protective Girlfriend: Katara become one to Zuko after he got shot by lightning, although by that point in the story she wasn't his girlfriend. Justified that Zuko was defenseless at the time and she was worried about assassins taking advantage of that.
Villain with Good Publicity: Subverted with Ozai; Fire Nation colonials don't trust him, and Fire Nation old guard and the elite generally think Ozai's completely nuts. The only ones who still want him on the throne are those who directly profited from Ozai's being there, or just consider him a "better quantity" than either the now-psychotic Azula or the unknown element Zuko.
We Were Rehearsing A Play: Jet and Zuko say they were acting out the fight scene in the Tragedy of Oma and Shu, not getting into a street fight, in an effort to avoid jail time.
Wham Episode: Aang disappearing before the comet, the Gaang were freaking and thinking that Aang might have abandoned them.
What Could Have Been: Katara's Character Arc of her training to become a doctor was going to address dealing post war racism, the author decided to abort the arc because she couldn't write it with the delicacy and tact the issue deserved.
What Measure Is a Mook?: In-Universe, the Siege of the North killed off many Fire Nation naval soldiers, a lot of them from Ember Islands. The Gaang, excluding Zuko, didn't realize the human cost until seeing a memorial service on Ember Island for the naval soldiers lost in the Siege. Zuko saw the dead bodies while floating on a raft at sea. Aang is left unaware of what he done until the worst possible time.
Word of God wondered where Appa went during the Agni Kai, but justified that Katara and Zuko must have put him somewhere far away from the site since he's afraid of fire.
Averted with Hawky. Per canon, Hawky, the messenger hawk Sokka bought did not show up after 'The Runaway'. In Not Stalking Zuko it is revealed taht he returned during the Gaang's stay at Ember Island with a reply and was sent back with a reply to THAT soon after.
What the Hell, Hero?: Katara does NOT accept Aang's lion turtle excuse, she calls him out for abandoning them in their most critical hour.
Everyone calls out on Aang for sparing Ozai and destabilizing the Fire Nation power structure.
You Are Not Alone: It's implied this was what finally convinced Zuko to become Fire Lord, that Iroh would be helping him rule.
Your Approval Fills Me with Shame: Arnook congratulates Aang for both his sparing Ozai — explicitly because of this causing major political instability amongst the Fire Nation — and for his slaughter of the Fire Nation navy fleet. Aang, who believed that he never killed people, is not pleased and horrified.