[[foldercontrol]]

[[folder:A]]

* ABoyAndHisX:
** "Abner Come Home" from season one was about Arnold and his pet pig Abner.
** Season two gave us "Harold's Kitty", where Harold takes in a kitten initially assumed to be abandoned and names it Cupcake.
** "Helga's Parrot" from season four could be construed as a rather twisted take on A Boy, A Girl, and Their Parrot.
* AbortedArc: In "Helga's Show", Helga was able to do impressions because P.S. 118 just got a new student lounge. But after that episode, the lounge is neither seen nor mentioned again.
* AbhorrentAdmirer:
** Curly has an obsessive infatuation with Rhonda and never accepts that she's not interested.
** Brainy is a milder version of this trope; his presence annoys Helga to no end but all he really does is breathe down her neck.
*** And somehow [[OffscreenTeleportation always manage to show up behind her]].
* AbsurdlySpaciousSewer: In ''Sewer King", Arnold and Gerald encounter the Sewer King in the sewers, which are way more spacious than real life sewer systems.
* AbusiveParents:
** Bob and Miriam Pataki, but especially Bob, are abusive to their daughters in different ways. Bob has a horrible temper, is extremely authoritarian, and is [[WhenYouComingHomeDad otherwise obsessed with his work]], while Miriam is always either loopy or [[TheAlcoholic passed out on the couch with]] "[[FrothyMugsOfWater smoothies]]." The two of them pay no mind to Helga, always calling her by her sister Olga's name ([[ParentalFavoritism whom they dote on whenever she's around]]). Meanwhile, their EducationMama tendencies turn Olga into a neurotic mess from having to be perfect for them, to the point that [[TheBGrade getting a B on an otherwise flawless report card]] causes a nervous breakdown. "Helga On The Couch" delves into this at length.
** The Jolly-Olly Man's father/boss has him ''firmly'' under his thumb, causing him to loath his job and [[ChildHater the children he has to serve]].
* AccidentalMisnaming: Helga's father always calls her by her sister's name, Olga. He also occasionally incorrectly refers Arnold as "Alfred".
* TheAce:
** Helga's "perfect" college-aged sister Olga only ''looks'' perfect, but she's dangerously neurotic and melodramatic thanks to having to live up to her parents' constant attention and high standards. She even tells Helga once she'd rather be TheUnFavorite since that would let her be free like Helga is.
** Lila's a parody of the character being perfect at everything they do, as well as a general ParodySue.
** Arnold himself can do anything. By the time of the movie, most of the neighborhood believes he can save them from having to sell up and move. And he does.
* AcidRefluxNightmare: In "Helga Sleepwalks", Helga started sleepwalking after eating pork rinds.
* AcquaintedWithEmergencyServices: In Season 5, "Stuck in a Tree", when Arnold, [[TheJinx Eugene]], and Harold are [[ExactlyWhatItSaysOnTheTin stuck in a tree]], they see Chocolate Boy and tell him to get help from the fire department. Eugene tells Chocolate Boy to mention him to the firefighters because they know him from previous rescues. Arnold has a "Why am I not surprised?" reaction to what Eugene said.
-->'''Arnold''': ''(to Chocolate Boy)'' Go to the fire station, tell them we're stuck in a tree, and we need help getting down.\\
'''Eugene''': Tell them Eugene sent you. They know me. They rescued me many times before.
* {{Acrofatic}}: Harold sure can move quickly for a big guy.
* ActuallyNotAVampire: In "Sid The Vampire Slayer", Sid spends the whole episode believing Stinky is a vampire and tries to get proof. When he confronts Stinky, he has a perfectly logical explanation for everything and Sid leaves feeling stupid. Cut to later that night, where we see Stinky, talking to a bat and looking suspiciously like a vampire!
* AdaptationExpansion: Arnold originated in a series of [[StopMotionAnimation claymation]] shorts for ''Series/SesameStreet'', albeit as much different character who [[MrImagination frequently daydreamed]]. Needless to say, it was nothing like what it would become.
* AddictionDisplacement: Chocolate Boy gives up chocolate in his spotlight episode and starts eating radishes instead.
* AdultsAreUseless: Zig-Zagged. How helpful adults are in solving the kids' problems depends on what is needed for the episode's plot.
** Exemplified on "Longest Monday". The entire [[KidsAreCruel Fifth Grade Class]] participates in a sadistic ritual in slamming the Fourth Graders into trashcans or dumpsters, often rolling them down hills while IN the trashcans regardless of traffic. Not to mention breaking into the Fourth Grader's refuge and even preforming the act ''on a bus''. Where are the parents, schoolteachers, staff? Unknown, ''no adult is shown at all in the episode''.
*** TruthInTelevision. Adults often overlook yearly traditional hazing rituals in the same vein as the episode, provided that they aren't ''too'' violent.
* AesopAmnesia:
** Rhonda apparently learns not to be a self-centered libby ''several'' times, Olga seems to forget all about her past visits to the Pataki household with each visit, proclaiming her wish to better connect with Helga while unconciously annoying her in all the usual ways.. In one episode, Harold gains new confidence when he learns just how smart he can be if he puts some effort in... next we see him, he's back to being the ButtMonkey crybaby of the class.
** Justified with Miriam. She learns to be a better mother a couple times; but a couple other episodes make it seem like she's back to her old ways. She relapsed.
** At least two episodes had the characters involved immediately forget their aesops before the episode even ended, in one Rhonda isn't invited to a party because she chose to alienate everyone else, at the end of the episode she shows she realizes this was wrong, but before the episode ends quips that the next day she'll be 'popular' again and not a geek like the rest of the party who alienated her for her alienating them, thus showing she really learned nothing. Harold had one where he gained a lot of extra weight and worked hard to lose it, at the end of the episode after losing all the excess weight (not all of it, he was still the BigEater of the show) he immediately accepts a bet of eating 50 ice cream bars, the same act that caused him to feel bad about himself at the start of the episode.
** "Olga Comes Home" had Helga and Olga share a touching moment when Olga reveals she ''hates'' all the attention and being, as she describes 'Some sort of wind up doll' for their parents and admitting that she wishes she was neglected like Helga. Both Helga and Olga have apparently forgotten this since their main conflict in ''every'' episode is Olga's perfectionism and Helga forgetting how 'good' she has it.
** In "Helga's Masquerade" Helga learns that she does not need to act exactly like Lila to be liked by Arnold, but generally acting nicer will earn her his love. In her next appearances, she's back to jeering at Arnold.
** Similarly, Arnold will often forget Helga's acts of kindness or getting along with him by the time of the next lesson, acting surprised as if he sees her being nice for the first time in his life.
* AffectionateNickname:
** Olga always addresses Helga as "Baby Sister," and when she hangs out with Lila in one episode (as part of the "Big Sis, Little Sis" charity) addresses her as "Little Sis."
** Grandpa always calls Arnold "Short Man". [[spoiler:Craig Bartlett has confirmed that it's supposed to be a pun on his surname, "Shortman".]]
* AirVentPassageway:
** Dino Spumoni crashes the concert of an incredible [[FreudianSlip stimulation]] of himself by crawling through an air vent.
** Helga sneaked in and out of the Sunset Arms through an air vent in more than one occasion.
* TheAlcoholic: Helga's mom, Miriam, according to Craig Bartlett, but this could only be implied thanks to Nickelodeon's {{Media Watchdog}}s. She drinks a lot of "[[FrothyMugsOfWater smoothies]]," talks in a tired, slow voice, looks extremely depressed, is oblivious to her surroundings, forgets things, doesn't drive anymore (and when she did on an episode where Helga and Miriam try to bond during a road trip, she drove rather erratically), and is often found asleep (usually in strange places, like behind the couch or on the living room table). When making a "smoothie", she grabs a bottle of hot sauce.
** To enforce this, Helga never seems to find her mother's behaviour unusual or incorrect, implying that it's been going on for so long that to her, it's perfectly normal.
** If the spinoff ''The Patakis'' had been made, it was said that Miriam would be attending AA.
** It has been suggested that Helga merely ''refers'' to the booze as 'smoothies' for reasons ranging from basic ignorance, to being told to do so.
* AllJustADream: [[spoiler: "Arnold Visits Arnie" ends with the revelation that Arnold only dreamed about visiting his cousin Arnie.]]
* AllLoveIsUnrequited:
** In "Arnold Visits Arnie", Arnie has a girlfriend Lulu who is madly in love with Arnold, who has a crush on Hilda who falls in love with Arnie.
*** Which is just a bizarro rendering of the usual LoveTriangle between Arnold, Helga and Lila. (Which also includes Brainy having a crush on Helga.)
*** It gets better; see LoveDodecahedron on [[HeyArnold/TropesJToP Tropes J to P]].
** Arnold had an unrequited crush on Ruth in the first season.
** Arnold's unrequited crush on his substitute teacher in "Crush on Teacher" is an understandable case, given the age difference between them.
** Rhonda is stalked by Curly a lot, too.
* AllThereInTheManual: The sixth book of the series Hey Arnold! [[http://www.amazon.com/Arnold-Arnolds-Files-Groening-Bartlett/dp/0439381495/ref=pd_sim_b_3 Arnold's E-Files]] confirms that Brainy is in love with Helga and that he has HiddenDepths.
* AlmaMaterSong: P.S. 118 has a particularly unpopular school anthem.
* AlphaBitch:
** Rhonda very often uses her social status as an excuse to be stuck-up and snobby.
** The sixth-graders that use Phoebe also fit into this category; they also move Rhonda to the back of the bus when she gets glasses.
* AluminumChristmasTrees: Hedy Lamarr, the actress Grandpa always talks about was a real actress in the 1930s and 40s.
* AmbiguousDisorder:
** Arnie, Arnold's cousin. Hobbies include reading ingredient labels, counting things, and collecting lint. He also doesn't seem to know social norms; he asks Rhonda if she wants to see his ball of lint.
** Curly definitely has a few screws loose, considering how unpredictably hostile and manic he can act.
** Crappy life aside, there's evidence to suggest that Helga has some kind of disorder herself.
* AmbiguouslyBi: Gerald has shown interest in a few girls in the series (most notably Phoebe) but in the movie, he seems to be a bit infatuated on Scheck, mentioning how good he looks in that suit at least three times.
* AmbiguouslyGay:
** Eugene. He has a room decorated with [[TastesLikeDiabetes rainbows and unicorns]], and often takes interest in anything related to dancing and musicals.
** Mr. Simmons is voiced by an openly gay actor, has an effeminate personality, likes theater and a man who may or may not be his partner shows up in "Arnold's Thanksgiving". Craig Bartlett states that he is in fact gay, but a kids show at the time could never openly state so.
** Principal Wartz apparently lived with another man in "Sid's Revenge", though it's unclear if this was a partner, a roommate, or simply a visitor. In another episode, Wartz was shown to be excited about a singer mostly popular among young girls. He also hangs out with Mr. Simmons lot, even briefly dancing the tango with him in "April Fool's Day".
** Miss Slovak, the original fourth grade teacher is elderly and unmarried. She also retired to pursue a career in professional golf (golf being a ButchLesbian stereotype).
* AnAesop: Quite a few episodes had important lessons to teach.
** "Helga on the Couch" taught kids that seeing a shrink isn't a negative thing.
** "Mr. Hyunh Goes Country" says that sometime people who are incredibly talented [[DoingItForTheArt don't want to be rich and famous for it]].
** "Suspended" teaches that certain punishments can be worse than you anticipate them to be.
* AnimationBump:
** The first season was handled by Creator/HongYing and Creator/WangFilmProductions. While the animation quality wasn't ''bad'', it just looks slightly off compared to the rest of the series, which was animated by Creator/Saerom.
** At the beginning of Season 4, the show switched from cel animation to digital ink and paint.
** Another animation bump appeared right at the end of the series, when ''Hey Arnold! The Movie'', ''April Fool's Day'' and ''The Journal'' were being made. All three of them (particularly the movie) look considerably better than the rest of the series.
** The test footage made for ''Hey Arnold! The Jungle Movie'' [[https://vimeo.com/36323643 looks even better]] than the first movie. The real footage from the rebooted ''Jungle Movie'' looks even better than that!
* AnnoyingYoungerSibling: Gerald's little sister, Timberly. A more realistic example. According to Jamie-O, Gerald is this to him, but it's incredibly hard to feel sympathy for him when Jamie-O is one of the biggest {{Jerkass}} characters of the series. Jamie-O does eventually decide that Gerald isn't as much of an annoying younger sibling after he points out that his relationship is parasitic.
* AnguishedDeclarationOfLove: In ''Hey Arnold! The Movie'', Helga gives one to Arnold along with a [[TheBigDamnKiss passionate kiss]]. [[spoiler:Then revealed at the end that she denies it.]]
* ArsonMurderAndJaywalking:
** The rules at the aquarium include no guns, no knives, "NO SUSHI CHEFS!", no plastic explosives, no diving in the shark tank, "and most importantly -- NO SKATEBOARDS!"
** In "Harold the Butcher," when Harold has to see his rabbi because he stole a ham from Mr. Greene's butcher shop, the rabbi tells Harold that stealing violates one of the Ten Commandments. However, he goes on to say "most importantly, you stole a ham," referring to Jewish dietary laws. Apparently, if Harold would have stolen some lamb or some other food permitted by the Torah, Harold's sin wouldn't have been as bad.
* ArtEvolution:
** Faces became more detailed and expressive as the show went on (particularly Grandpa's). Arnold's head looked more like a blimp at first, but then became taco-shaped. Helga's pigtails got thicker and shorter over time and her ugliness was toned down. And for most characters, their arms became thicker and their necks got shorter.
** The long gap between the series and ''The Jungle Movie'' has allowed for [[http://sev.h-cdn.co/assets/16/29/768x850/gallery-1469204388-hey-arnold.jpg another]]. Arnold now wears a dark blue jacket over his outfit, the plaid shirt no longer resembles a kilt and he appears slightly taller. Gerald's sweater has been replaced with an otherwise identical hoodie, his hi-top fade is shorter and has a more angled look to it (he also looks and sounds much younger than before). Helga's nose is smaller, her pigtails are more rounded, her dress is a lighter shade of pink with a darker pink stripe over the red one (which is now at the very bottom) and she appears to be [[ShesAllGrownUp developing breasts]] (as are most of the other girls). Phoebe seems to be the most drastically changed so far; her hair is longer, her top knot is larger and her baggy sweater has been replaced with a white top, blue jacket and light blue skirt. And all of the mentioned characters have different, more colorful shoes than before.[[labelnote: Some other changes]] Sid's undershirt is now a green v-neck, Stinky wears a brown and mustard yellow bowling shirt, Harold's blue shirt is missing the "H" on the left breast area, Rhonda's top has changed from red to indigo and she now wears a red jacket over it, Eugene has thicker eyebrows, Lila's green shoes are now brown cowboy boots, Nadine has visible eyelashes, Grandpa Phil now has a cardigan sweater, Stoop Kid now wears earrings the list goes on and on... [[/labelnote]]
* AsianAndNerdy: Phoebe is Asian and very intelligent.
* AsideGlance: Arnold looks toward the viewer at the end of "Arnold Saves Sid" [[spoiler:He looks directly at the screen though.]]
* AtrociousAlias: After Eugene manages to wreck his and Arnold's go-karts in the go-kart episode, they decide to combine their karts for the big race. Eugene and Sid argue over which name from the original karts to use for the new one when Stinky suggests combining their kart names. Cue "The Mauve Avenger", which everyone else absolutely hates. Apparently naming the kart its other combination, "The Dark Storm," never crossed their minds.
* AxCrazy:
** Curly is definitely a dangerous psycho. One episode mentions that he once bit off the head of a live chicken, though he insists it was only that one time.
** Arnold fakes being insane to scare off Harold from beating his ass in the original pilot and "24 Hours to Live".
[[/folder]]

[[folder:B]]
* BackForTheFinale: A number of one shot minor characters will be returning for ''The Jungle Movie'', such as Stoop Kid and the Pigeon Man.
* BackToSchool: Arnold's grandpa does so in "Back to School", passing fourth, fifth, and sixth grades all in one episode.
* BadHumorTruck: The Jolly Olly Man is a downplayed example. He is an ice cream man and he's far from being a pleasant person, but he's more of an asocial jerk than evil.
* BarbieDollAnatomy:
** Arnold and the other boys are shown shirtless in a few episodes and none of them have nipples.
** Another example is in "Rhonda Goes Broke", where Rhonda's sweater has a large tear in the chest area, yet still doesn't expose anything.
* BareYourMidriff:
** Olga and Lila's counterpart Lulu wears an outfit that leaves her navel exposed.
** Olga's outfit in "Student Teacher" is an exception--a longer version of her signature plaid miniskirt and a black sweater. However, there are frames where she appears to skirt the line a bit.
* BeachEpisode: "Summer Love" has the characters go to the beach.
* BeautyBrainsAndBrawn: Lila, Phoebe, and Helga are respectively a beautiful girl, an intelligent girl, and a girl who relies on physical force.
* BeeAfraid: "Helga's Boyfriend" has a scene where Helga gets attacked by bees at the park.
* BefriendingTheEnemy: Some episodes involving Harold, who is a bully to the other kids in his grade are frequently like this. Arnold being an AllLovingHero befriends Harold in multiple episodes. Even deciding not to rat out on him to the principal in one "Full Moon", and helping Harold lose a ton of weight he gained in "Weighing Harold".
* BeneathTheMask: Helga only expresses her feelings for Arnold when alone. (Well, alone with Brainy sneaking up behind her, anyway.)
* BetaCouple: In certain ShipTease episodes, Gerald and Phoebe would hook up in the background. And interview with Craig Bartlett stated that had ''[[SpinOff The Patakis]]'' gone through, Gerald/Phoebe would've been the "cool couple" to contrast with the somewhat dysfunctional long-distance relationship of Arnold and Helga.
* BewareTheQuietOnes: Discussed at the end of "Curly Snaps."
-->'''Mr. Simmons:''' I think we all learned a valuable lesson here today.
-->'''Helga:''' Yep. Don't ever trust the quiet ones. They'll go bonkers and hole up in the principal's office.
* TheBGrade: "Olga Comes Home" had Olga spiral into a depression over Helga changing one of the perfect grades on her report card into a B.
* BigApplesauce: The city the show takes place in is pretty obviously based on New York, Brooklyn in particular. Craig Bartlett states that there are generous bits of UsefulNotes/{{Seattle}} and Portland, OR mixed in as well.
* BigBrotherBully: Gerald's big brother Jamie-O is often picking on him for no reason.
* BigDamnMovie: In spades.[[note]]There's a reason why this trope was originally called "Why Is Arnold Saving Something".[[/note]] While the regular series is purely SliceOfLife and features down-to-earth problems faced by each individual character[[note]]The only episodes that could be described as having an action scene are "Runaway Float" and "Save the Tree".[[/note]], the movies are an entirely different deal.
** ''Hey Arnold! The Movie'' is an expanded version of "Save the Tree", featuring Arnold and Gerald sneaking into a corporate building using spy gadgets, Helga revealing her secret love for Arnold, the main characters on a runaway bus, the overpass behind the boarding house being blown up, underground explosions, and an army of bulldozers.
** The upcoming ''Jungle Movie'' is set to be even bigger, featuring no less than a trip to the uncharted jungles of San Lorenzo to find the titular character's [[ParentalAbandonment long-lost parents]] while facing a vicious crew of river pirates, and encountering the mysterious Green-Eyed people. Also, Arnold and Helga finally [[RelationshipUpgrade getting together]].
* BigEater:
** Harold frequently eats lots of food.
** Seymour, as revealed in "Eating Contest", is able to eat an assload of ice cream in one sitting despite his small size. However, [[spoiler: Arnold beats him]].
* BiggerOnTheInside: As seen in "Phoebe Cheats" Phoebe's house has several rooms that look like they should be in a mansion, like a sparring room and a jacuzzi room.
* BigStormEpisode: "The Flood" had the kids dealing with a flood happening at Hillwood and endangering them while they were at school.
* BigThinShortTrio: Harold, Stinky, and Sid frequently hang around and are obese, skinny, and short respectively.
** Sunset Arms boarders Mr. Huynh (big), Oskar (thin), and Ernie (short) to a lesser extent at times.
* BigWhat: "Spelling Bee" has Bob Pataki holler "What" in response to Helga deliberately screwing up spelling her word to throw the spelling bee.
--> '''Helga''': Qualm. Q-u-a-'''l'''-...''(looks at her father)''...-x?
--> '''Bob''': WHAT?!
* BigLippedAlligatorMoment: An in-universe example in "The Flood," when Helga catches Principal Wartz attempting to dance the salsa while she was trying to break out of the school. The characters-in-question even agreed that [[LetUsNeverSpeakOfThisAgain they'd never speak of it again.]]
--> '''Principle Wartz''': This moment never happened.
--> '''Helga''': Gotcha.
* BirdsOfAFeather: Olga and Lila get along well in "Big Sis" due to both being cheerful and perfect on the outside, but troubled on the inside.
* BittersweetEnding: There are a few episodes with bittersweet endings.
** "The List" ends with Arnold failing to do any of the objectives on the list of things to do for the ultimate weekend, but his grandmother helps him realize that he shouldn't be upset over it.
** "Eugene's Bike" ends with Arnold upset that his attempts at giving Eugene a good time have all ended in disaster, but Eugene forgives him because he still enjoyed the moments they had in spite of the misfortunes he suffered during them.
** "Pigeon Man" ends with the Pigeon Man forced to leave Hillwood, but he parts with Arnold on good terms and even hopes that he'll find another kid like him in the next place he goes.
** "Crabby Author" has Arnold disillusioned by finding that his favorite author has become a bitter recluse, but is cheered up to learn that telling her that he still considered her his favorite author has inspired her to get back to writing books.
** "The Journal" has Arnold learn why his parents have gone missing since he was a baby, but he also finds a map of San Lorenzo, which gives him hope of being reunited with his parents.
* BizarroUniverse: "Arnold Visits Arnie" had Arnold [[spoiler:dream of]] visiting his country cousin Arnie and finding that his rural town has polar opposites of Arnold's friends.
* BlackBestFriend: Gerald is black and Arnold's closest friend.
* BlindBlackGuy: One of the subway passengers in "Das Subway" is a black man who happens to be blind.
* BlondeBrunetteRedhead: Helga, Phoebe, and Lila have blonde, brunette, and red hair respectively.
* BodyWipe: in "Wheezin' Ed" near the end where Harold is rolling, and his butt fills the screen before running over everyone.
* BornUnlucky: Eugene could practically serve as the TropeCodifier (it doesn't help that he was born on Friday the 13th). See also ButtMonkey.
* BottleEpisode: "Stuck in a Tree" consists mostly of Arnold, Harold, and Eugene being stuck in a cherry tree with very little changes in scenery.
* BreakTheHaughty: Rhonda constantly gets her comeuppance for being rude and arrogant to the other kids. There are at least three different episodes dedicated solely to the idea ("Rhonda's Glasses", "Polishing Rhonda", and "Rhonda Goes Broke").
* BrickJoke: During Helga's dream sequence in "Magic Show", she finds that Phoebe became best friends with someone named Gloria, who dresses the same as Helga but looks sweeter and cuter. Come "Helga's Boyfriend", and Stinky ends up dating Gloria and proves she actually exists, which stumps Helga.
* BrokenAesop: In "Hookey", Arnold and Gerald skip school but their fear of being found out interferes with any fun they might have had. Eventually, they go to school only to learn that there was a surprise carnival day. This weakens the Aesop as skipping school is wrong because you miss class, not because you miss a fun day. The "weakness" of the episode's moral is [[LampshadeHanging Lampshaded]] at the end.
* BrokenPedestal:
** In "Eugene Goes Bad", Eugene finds that his idol "The Abdicator", an [[NoCelebritiesWereHarmed Arnold Schwarzenegger-esque]] ActionHero is not a real ActionHero, but a fictional character played by a JerkAss that's [[NiceCharacterMeanActor obnoxiously spoiled, bosses the staff on the set around]], and [[StuntDouble doesn't do his own stunts]]. Upon finding this out, Eugene does a temporary FaceHeelTurn that ends when the actor saves him from falling to his death, showing that, for all his flaws, he's a fundamentally good person who cares about his fans.
** In "Pre-Teen Scream", Phoebe gets to meet pop singer Ronnie Matthews, whom she idolizes for his lyrics which she thinks are deep and meaningful. She's devastated when it turns out he doesn't write or even sing his own music--he just gets paid to lip-sync and pretend to play the guitar. Simultaneously inverts the trope, as this causes Helga to admire him due to how he's managed to make so much money scamming people.
* BuffySpeak: Helga's description of Ruth in "Arnold's Valentine" has her resort to making up words.
-->'''Helga''': She's nothing but a stuck-up, sixth grade-y, training bra wearing, brace-y faced, [[DepartmentOfRedundancyDepartment sixth grade-y...sixth grader!]]
* BullyingADragon: Several episodes deal with people (usually Sid and Stinky), teasing either Harold or Big Patty, either of who can and will beat the crap out of them in retaliation.
* ButForMeItWasTuesday: A heartwarming example--in the Veterans' Day-special, it turns out that Gerald's is Vietnam War-veteran. However, he was sick with the flu during most of basic training, so he was unable to partake in any actual combat and mostly worked as an office clerk--in fact, the only real action he saw was when he once happened to come upon a fallen soldier who had a severe leg wound. Gerald's dad explains that he used some spare files to create a makeshift bandage for his leg--Mr. Johansen didn't think anything of it (he was just helping someone who happened to really need it). Twenty years, while Gerald and his dad, with Arnold and his Grandpa Phil in tow, are in Washington DC at the Vietnam War-memorial for soldiers, they run into the same man that Gerald's dad had saved in Vietnam--the man reveals himself to be named Private Miller and explains to Gerald's dad that if he hadn't done what he did to help in the war, he would've bled to death. Private Miller (who's with his wife and kids) adds that he's been waiting twenty years to personally thank him for ultimately saving his life.
* ButNotTooForeign: Phoebe has a Japanese dad and a white mom. Plus, Phoebe's last name, Heyerdahl, certainly isn't Japanese - unless her dad is only of partial Japanese descent.
* ButtMonkey:
** Eugene constantly gets injured or subjected to misfortune in just about all of his appearances.
** Arnold is not completely safe either (particularly if Helga's involved), and as Eugene, he doesn't have a too hard time handling his problems. This makes him into a NoRespectGuy.
** Sid, Stinky and Harold to a lesser extent than the former and latter.
** Brainy, at the hands of Helga. Helga backhands him every time she notices him.

[[/folder]]

[[folder:C]]
* CallBack: As shown by ''just'' the first teaser clip released for it, ''The Jungle Movie'' has a lot:
** [[spoiler: A number of the scenes in the video made for the contest to go to San Lorenzo in ''The Jungle Movie'' are (remastered) scenes from the show's original run. In order, we have Arnold and the kids cleaning up "The Vacant Lot", Arnold getting Nadine and Rhonda to reconcile with each other in "Best Friends", Arnold going to comfort Mickey Kaline in "The Baseball", Arnold giving Eugene a bike in "Eugene's Birthday", Harold giving up Thurston the kitten in "Harold's Kitty", Arnold running off some muggers in "Mugged", Arnold dressed as a banana for the school play in "Downtown as Fruits", Arnold being crazy in "24 Hours to Live", and Arnold running with Grandpa Phil in "Steely Phil".]]
* TheCameo: During later seasons, it's pretty common to see past/minor characters in crowd shots and backgrounds. ''Hey Arnold! The Movie'' has a ton of these during its first act.
* CampGay: Mr. Simmons is a toned down version of this, as while he is confirmed to be gay, his effeminate traits and mannerisms aren't blatant.
* CassandraTruth:
** In "Girl Trouble", Arnold is fed up with Helga's bullying and goes to his Grandpa for advice. Phil guesses that the reasons she bullies him is because she likes him, pointing out that a girl named Gertie (who turns out is Arnold's Grandmother) did the same thing to him when he was younger. Arnold dismisses this theory.
** [[spoiler: In "Married", Rhonda repeatedly tells Arnold that he will marry Helga (via a marriage predictor). The only one who believes it is Helga, but as per the word of Craig Bartlett, they do get married in the future.]]
* CastOfSnowflakes: The art style makes good use of creative head shapes and various body sizes and proportions to make the characters distinctive and not resort to reusing character designs.
* TheCatCameBack: Subverted in "Phoebe Cheats" when out of guilt Phoebe tries to dispose of a trophy she didn't earn. There are logical reasons why it keeps coming back into her possession, but she doesn't see them and she thinks it's moving by itself.
* CatchPhrase:
** Helga often says "Criminy" when she is frustrated or annoyed.
** Grandpa's - "Never eat raspberries".
** Stinky always either says "this bites" or "this really bites" when something upsets him.
** Sid says "boy howdy" fairly often as well.
** Harold often grumbles "Madame Fortress Mommy'." Whenever he's scared he usually cries out [[IWantMyMommy Mommy]]!
** Gerald has "Are you thinkin' what I'm thinkin'?" He apparently got it from his father, who does it to Phil in the Veterans Day episode.
*** In the April Fool's episode Arnold borrows it and turns it around:
--> '''Arnold:''' I think you're thinking what I'm thinking.
--> '''Gerald:''' ''(whispers in Arnold's ear)''
--> '''Arnold:''' That's even better than what I was thinking.
** Gerald also has "You're a bold kid, Arnold... a bold kid." He even lampshades it when [[BorrowedCatchPhrase Arnold says it to him.]]
--> '''Arnold:''' You're a bold kid, Gerald.
--> '''Gerald:''' Hey, that's my line.
** Eugune has "I'm okay..." which was "I'm fine" in earlier episodes.
** Then there's Mr. Hyunh with always calling some of the show's more eccentric characters "creepy" (which they admittedly are).
** The Jolly Olly Man has "Who's laughing now eh? WHO'S LAUGHING NOW!?"
** Harold has a tendency to say, "I was hungry!" whenever people look at him for eating something he shouldn't.
* CaughtOnTheJumbotron: Arnold and Gerald are caught on the big screen at a baseball game while skipping school in "Hookey", much to their horror.
* CelebrityIsOverrated:
** Stinky doesn't want to be an idiot in soda commercials in "Stinky Goes Hollywood".
** "Mr. Hyunh Goes Country" is about this: Mr. Hyunh could have been the next big country music star, but after tasting fame, he gives it up because he prefers his normal, simple life.
** In "It Girl": Helga is against modeling for Johnny Stitches from the start, only doing it for the money and the free stuff. Seeing everyone wearing her dress and bow (even some boys are wearing it) pushes her over the edge. So she tries to get fired by shoving a model during another one of Stitches' shows, then by spitting in front of the press. Realizing that being mean only makes people love her more (since Helga's nastiness is much of her image), Arnold suggests that she try acting nice at Fashion Week. And it works.
* CelebrityParadox: In the ''WesternAnimation/HeyArnold'' universe Dino Spumoni is a [[NoCelebritiesWereHarmed stand-in]] and AffectionateParody of Frank Sinatra and Dean Martin, but in Dino Checks Out it shows that Dino was a member of the Creator/RatPack along with them.
* CelebrityStar: Randy Travis in "Mr. Hyunh Goes Country". Voiced facsimile Travis Randall, and the titular Mr. Hyunh (when singing).
* CerebusRetcon: Originally Helga's situation with her family was PlayedForLaughs. Helga's mom falls asleep all the time while making "[[FrothyMugsOfWater smoothies]]"? Hilarious. Helga's dad always calls her by [[ParentalFavoritism her sister's name]]? Hysterical. Neither of them really pay attention to her? Knee-slapping. Then came the episode "[[ADayInTheLimelight Helga on the Couch]]" and her family's neglect of her was shown in a far more serious light.
* CharacterDevelopment: There was much character development through the series, with Harold and Helga's developments into being nicer and more sympathetic characters being the most apparent cases.
** In fact, Arnold is probably the character that got the ''least'', and what little he ''does'' get usually pertains to his feelings for his LoveInterests. After pining after Ruth [=McDougal=] for most of the first season, he finally goes on a date with her in "Arnold's Valentine" and almost instantly loses interest after spending time with her. His more notorious attraction to Lila, which began in season 3 with "Arnold & Lila", actually comes to an end in "Timberly Loves Arnold", late in season 5. Tellingly, in "Eugene, Eugene!", which immediately followed "Timberly Loves Arnold", he shows absolutely no interest in her - even in a scene when he and Stinky are watching her audition (while Stinky fawns over her). Lila also has no more speaking parts after this and it's been confirmed that she will not appear in ''The Jungle Movie.'' [[spoiler: This since has become a case of either LyingCreator or ChangedMyMindKid, as she can be seen in the SDCC clip, but [[DemotedToExtra most likely won't do anything important]]]]
* CharacterizationMarchesOn:
** Remember when the Jolly-Olly Man used to be a simple, nameless, smiling ice cream man and not a total psychopath?
** Remember when Arnold was a chronic daydreamer?
** Remember when Harold was a {{Jerkass}} and less of a JerkWithAHeartOfGold?
** Remember when Stinky was a bully and sidekick to Harold? Furthermore, remember when he wore those spiky wristbands?
** Remember when Sid wasn't a paranoid nutcase? The guy even gained episodes dedicated to him because of it.
** Remember when Rhonda wasn't rich?
** Remember when Helga was so unsympathetic that her failures and neglectful home life were amusing? And her crush on Arnold was of the [[StalkerWithACrush stalker]] variety? Well, that last part never changed much, but she did eventually commit several [[ActOfTrueLove acts of true love]].
* TheChewToy:
** Eugene, the AnthropomorphicPersonification of bad luck.
** Arnold's father Miles is pretty accident-prone too. Not as extreme as Eugene though.
** Pick an episode where Helga's secret is in danger of some sort, and you'll get an episode where the universe itself plots against her for eleven minutes straight.
* ChezRestaurant: Chez Pierre and Chez Paris who are ''right across the street from one another'', the better to aid any would-be TwoTimerDate.
* ChristmasEpisode: "Arnold's Christmas", where Arnold tries to reunite Mr. Hyunh with his daughter as his Secret Santa present.
* ChuckCunninghamSyndrome:
** Mr. Hyunh's daughter Mai was never seen again. Possibly justified - after all, she presumably had adoptive parents in the US, given that her father hadn't been in her life for about 2 decades. She is mentioned only once, in "Family Man".
** Ruth [=McDougal=] (the sixth grader Arnold had a crush on in the first season) mysteriously disappears towards the middle of the series. One could guess that she simply graduated from P.S. 118, since she was already in sixth grade, and Arnold never mentions her (or his crush on her) after the Valentine's Day episode in which Arnold tries to go on a date with both Ruth (who thinks she's seeing a famous poet named "Anonymous") and his French pen pal, Cecilia, and discovers that Ruth isn't all that bright or interesting to be around. In "What's Opera, Arnold?," she appears mainly for Helga to have a foil in Arnold's dream opera. Afterwards, she only cameos two or three times.
** Tucker, Coach Wittenburg's son. Appeared in one episode and was never seen or mentioned again. Odd, since Coach Wittenburg gets a few focus episodes. It's particularly glaring when one such episode deals with Wittenburg's estrangement from his wife. [[spoiler: He finally reappears in ''The Jungle Movie'' alongside his parents.]]
** Mr. Smith (the first season boarder whose face nobody sees) never appears after "Door #16"
** Lana Vail, the brunette woman who lived in the boarding house, also disappears midway through the first season, but shows up in background shots on occasion; for example, at the restaurant with the cockroaches in "Dinner for Four". Some sources say that her original characterization was considered too inappropriate for Nickelodeon[[note]]She would frequently flirt with Arnold, who is nine-years-old and would be creeped out by it.[[/note]] so they dropped her altogether.
** Mr. Purdy also disappeared after only a quick gag in one episode. The boarding house sure suffered a loss of business after season 1.
** Torvald seems to have completely disappeared after only a few appearances.
** Billy, a member of the geek ensemble introduced in "Eugene's Bike" disappeared without a trace after the first season.
** Inverted with Grandpa's sister Mitzi, who appeared out of the blue with no previous mention during the fourth season. However, she also never made any other appearances afterwards.
** Ludwig never appeared again after his debut episode despite the implication that he and Wolfgang would join forces from then on.
* CircleOfShame: This happens dozens of times. Often, several of the characters forming the circle were laughed at in an earlier episode, because KidsAreCruel.
* TheCityVsTheCountry: Lila moves from a farm to the big city and is immediately resented and made fun of by the other kids. Subverted when she stays in the city and the other kids warm to her.
* CloudCuckooLander:
** Arnold's Grandparents both tend to be very eccentric and prone to bizarre habits.
--> "Hey! Crazy lady! Come back here with my bulldozer!!"
** In the first season, Arnold himself was this way, being very quiet and introverted, with a tendency to frequently lapse into intense daydreams.
** Principal Wartz, too. During the flood, he dressed in Mexican garb and danced around, then climbed onto the school roof and started singing. He later quit his job as principal for an episode to seek a career as a singer.
* TheCollectorOfTheStrange:
** Helga's statue of Arnold made out of wads of ABC gum the boy threw away, doubles as a StalkerShrine.
** Arnold's cousin Arnie collects ''lint''.
** Ernie has his entire apartment filled with the last brick of each building he demolished (which is over 500). Amazing the extra weight hasn't caused his floor to give in.
* ComicBookTime: Several dates in the background show the series takes place in the mid-to-late 1990s. During "New Bully on the Block", the scoreboard said Gerald Field was founded in July 1997. A newspaper printed on October 9, 1998 appears on "It Girl", and the show Arnold and Helga appear on on their beach trip is filmed in July 22, 1999. Despite these dates being from 3 different years, very few characters are shown having birthdays, and none of the kids ever move on to the 5th grade. ''The Jungle Movie'' moves the timeline all the way to the 2010s, with Rhonda being shown taking selfies with a smartphone.
* CommunityThreateningConstruction: The BigDamnMovie, which has the residents of Arnold's neighbourhood banding together ([[HeelFaceTurn although some later than others]]) to prevent the neighbourhood from being razed and turned into a mall by a CorruptCorporateExecutive. This includes Arnold and Gerald going into a quest to find documents that show that the neighbourhood has historical significance.
* CompressedVice: Oskar's illiteracy. "Oskar Can't Read?" is the only episode where it comes up.
* ConsolationWorldRecord: [[spoiler: "World Records" has everyone in Hillwood try and fail to break a lot of world records, but end up breaking the record for the most record-breaking attempts to ever be attempted!]]
* ConspicuousCG: In the third act of ''Hey Arnold! The Movie'', the [=FTi=] helicopters, the bulldozers, Scheck's car, and Murray's bus are very clearly 3D models. They stand out because they aren't like that all the time. If you pay attention, you can see how in one shot, the bus/bulldozer is hand-drawn, while in the next it's 3D.
** Justified, since the movie ''was'' made in 2000-2001.
* ContinuityCavalcade: [[spoiler: A scene in ''The Jungle Movie'' features the neighborhood throwing Arnold a surprise party with many of the characters that he's helped over the years either attending and/or appearing in a video shown at the party, including folks like Pigeon Man, the Stoop Kid, Mr. Hynuh's daughter, Coach Wittenburg and his family (yes, even [[ChuckCunninghamSyndrome Tucker]]), Dino Spumoni...]]
* ContinuityNod:
** Lila mentions she gets sick on the big amusement rides in "Love and Cheese". After riding the coaster in "Timberly Loves Arnold" she's seen throwing up.
** There's a couple in the movie involving the episode "Dino Checks Out." Out of his album covers spoofing Music/TheDoors Strange Days is seen in Grandma's jail cell, and the Dino Impersonator is seen in the bar Arnold and Gerald sneak into.
** The premise of "Beaned" calls back to the plot of "Dangerous Lumber," showing that Arnold still has a perfect record for beaning people with baseballs. And the plot of "Dangerous Lumber" could be seen as continuing off of the event that kicked off "24 Hours To Live."
** In the episode where Arnold tries to help Chocolate Boy overcome his chocolate addiction Gerald mentions several of Arnold's past accomplishments which were all from past episodes.
--> "Helped Stoop Kid and The Pigeon Man, found Mr. Hyunh's daughter, saved Mighty Pete, stopped the teachers strike..."
* CoolBigSis: Olga tries to be a cool older sister to Helga, but Helga resents her most of the time. She gets along better with Lila in "Big Sis".
* CoolCar: Grandpa's vintage Packard; it was even the focus of "Grandpa's Packard".
* CoolLoser: In "Cool Party" Gerald is on the "geek" list. Subverted in that Gerald was only put on the "geek" list by Rhonda because [[DisproportionateRetribution he beat her for the position of Class President in 2nd grade]].
* CoolOldGuy: Arnold's Grandpa is a very good guardian to his grandson and will sometimes join in his grandson's pastimes.
* CoolOldLady: Arnold's Grandma occasionally is the one who helps Arnold save the day.
* CorruptCorporateExecutive: Sheck in the movie, who isn't above burning a historical document declaring the neighborhood where the main characters live as a national landmark just to build a huge mall.
** Technically that wasn't corruption, that was revenge. As he wanted to destroy that neighborhood because that's where his ancestor lost.
* CorruptTheCutie: Arnold's Grandpa after entering fifth grade becomes more prone to dishonest behavior.
* CovertPervert: In "Timberly Loves Arnold", [[PuritySue Lila]] says this immortal line:
-->'''Lila:''' That is, if Arnold doesn't mind making it a [[ItMakesSenseInContext threesome]].
* ComicTrio: Harold (Moe), Sid (Curly), and Stinky (Larry), especially earlier on, when Harold was more of a one-dimensional bully and Sid and Stinky were his flunkies.
* TheCowl: Hillwood's local superhero Monkeyman strives to fight for the good of all.
* CPRCleanPrettyReliable: Subverted and inverted at the end of "Summer Love" in which Helga gives Arnold CPR after being rescued in a "Babewatch" film shooting, only for her to [[KissOfLife give him a kiss]] which surprises Arnold.
* CrackDefeat: Subverted in "Family Man", where Mr. Hyunh worries that his new boss will pick an inferior cook as the new head chef of the restaurant he works at simply because he has a family, but Mr. Hyunh gets the position in the end precisely because he's a way better cook than the other guy.
* CrappyHolidays: "Arnold's Thanksgiving" has Arnold and Helga complain about their own Thanksigivings, but finding that Mr. Simmons' Thanksgiving is even worse.
* CrazyPeoplePlayChess: The Sewer King plays chess and is strongly implied to be out of his gourd.
* CreativeClosingCredits: Quite a few episodes (particularly special/serious ones) have their own unique credit music. Some episodes even have the credits playing over actual animation and dialogue ("Principal Simmons").
* CreepyChild:
** Curly, and his TroublingUnchildlikeBehavior sometimes comes to the point of high-potential AxCrazy. Upon finding that he wasn't assigned the Ball Monitor privileges that he anticipated for that week, he holed himself up in the principal's office with the balls, throwing them at anyone who tried to reason with him. He tried to get Eugene expelled simply because [[DisproportionateRetribution he ruined his favorite pencil]]. Curly's [[StalkerWithaCrush Stalker-iffic]] admiration of Rhonda intersects with this trope more often than not.
--->"SO HOW ABOUT A LOCK OF YOUR HAIR TO KEEP UNDER MY PILLOW?"
** Stoop Kid. The neighborhood kids are rightfully scared of him.
** To an extent, Arnie is a bit creepy as well.
* CurseCutShort: In "Ghost Bride", while Arnold is reading the epitaph of the titular Ghost Bride.
--->Arnold: Here lies Cynthia Snell. She lived her life and went straight to... I can't read the rest.
* CuteBruiser: Helga is 9 years old and still pretty capable of giving beatings to other people.
[[/folder]]

[[folder:D]]
* DarkerAndEdgier: In-universe in "Eugene, Eugene". The director deliberately changes the original happy ending of the play into a DownerEnding, to stimulate the BlackComedy fan crowd.
* DarkSkinnedBlond: Nadine. This becomes a bit more...somewhat plausible when you notice that in Parents Day, her dad is white and her mom is black.
* ADayInTheLimelight: Despite his name being in the title, there are more than a few episodes where Arnold has absolutely no connection to the plot at all.
** Indeed, by the end of the series, it's easier to count the secondary characters who ''didn't'' ever get an episode focusing on them[[note]]Sheena, Nadine (unless she was with Rhonda, like in "Best Friends" but that episode was more about Rhonda than her) Park, Joey, Brainy[[/note]]; practically every kid in Arnold's class and "permanent" member of the boarding house had at least one. Even Helga's parents had at least one each.
* DeadArtistsAreBetter: In an in-universe example, one episode involves Dino Spumoni faking his death to rekindle an interest in his music and raise his sales.[[spoiler: It works too well as a Dino-impersonator comes along, doing his songs and gigs, dates his former wife, and his dog loves him, and drives Dino jealous and reveals he isn't dead.]]
* DeadlyEuphemism: Grandpa and Jimmy Kafka exchange a bunch of these in "Old Iron Man" when they believe they're about to drown.
--> '''Grandpa''': We're going to Davy Jones' Locker!
--> '''Jimmy''': Kicking the bucket!
--> '''Grandpa''': Buying the water farm!
--> '''Jimmy''': Checking out of the Hotel of Life!
--> '''Grandpa''': And checking into the Hotel of Death!
--> '''Jimmy''': The Big Roundup!
--> '''Grandpa''': The Last Tango in Paris!
--> '''Jimmy''': The Last Tango in Paris? [[LampshadeHanging That's not a euphemism for dying!]]
--> '''Grandpa''': I know but it was my turn and I ran out of euphemisms and I didn't want to lose the game!
** In "Grandpa's Birthday", Grandpa uses the phrase "Buying the farm" to Arnold. Arnold takes it literally at first.
* DeadpanSnarker:
** Gerald will frequently make sarcastic remarks about the situation.
** Let's not forget Helga, who can snark with the best of them.
* DeanBitterman: Principal Wartz can be grouchy and unreasonable at times.
* DeceasedParentsAreTheBest: Arnold's parents, Miles and Stella, are assumed to be deceased. Whether they are or not, they fall squarely into the trope, having devoted their lives to working with and healing the inhabitants of remote jungles. In the ultimate saintly move [[spoiler: they left Arnold with his grandparents after being pressured to go on one last mission--and never came home.]]
* {{Deconstruction}}: Arguably for shows like Arthur and Recess. For in those shows, there is a memorable/colorful cast of characters, all with their own personality quirks. While that is present here in Hey Arnold, the quirks and traits that make the characters more or less memorable, are usually the result of some hidden neurosis, or psychosis. Some characters have even received therapy for said problems; only to regress to their former problematic ways at the story's end.
* DefeatEqualsFriendship: Subverted in the episode "24 Hours To Live" because even though Arnold never fought Harold directly, he still gained his respect after the "fight" sequence, through the way he ''got himself out of'' the fight.
* DemotedToExtra: After Arnold finally gets over Lila in "Timberly Loves Arnold[=/=]Eugene! Eugene!", she becomes a background character and never has another speaking role.
* DenserAndWackier: Later episodes became more comedic and off-the-wall in tone.
* DepartmentOfRedundancyDepartment: Coach Wittenburg repetitively overuses words.
* DependingOnTheWriter: A lot about the way the kids relate to one another change depending on the plot - which makes a bit of sense for grade school kids.
** Most obvious is how close the gang is: sometimes they're one huge tightly knit group of friends that hang around together with little to no friction ("Arnold's Halloween"; pretty much any time they play on the vacant lot), while other times they seem to have no problem with insulting/making fun of their friends. Generally, it's shown that Arnold's closest friends aside from Gerald are Harold, Sid, Stinky, and Eugene.
*** Notably, the TrueCompanions approach to the 4th graders is most often used in episodes where they go on some kind of adventure ("Ghost Bride") or are up against a common enemy ("New Bully on the Block"; "New Teacher"), and got a bit more common in general episodes as the show went on.
** Helga's relationship with Arnold - sometimes Arnold sees her as a bullying nuisance and doesn't seem to like her very much ("Girl Trouble"; "Summer Love"; "Married"; and ''particularly'' "Egg Story", so much that it seems out-of-character), whereas other times, it's evident that he is aware that her abrasive attitude is a cover of some kind and approaches her as a friend regardless of her behavior ("Helga vs Big Patty"; "School Play"; any episode where Helga has a family problem and Arnold gives her advice).
* {{Determinator}}:
** Helga will refuse to let any setback stop her, particularly when her secret is in danger of getting out. The climax of "Helga's Parrot" in particular has her single-mindedly driving herself through the roof to keep things under wraps.
** Brainy has been given {{Offhand Backhand}}s whenever he tries to be near Helga since the age of three…now nine, [[RunningGag he still does it]].
* DidntThinkThisThrough: Harold's plan to get a week off from school by intentionally getting himself suspended in "Suspended" proves to have a few holes in it. For starters, he intended to spend most of his time watching TV and eating junk food and didn't anticipate that the programs he wanted to watch would be interrupted by an emergency broadcast or that he'd currently be out of the kind of food he likes to eat. He also tried to hide the fact that he was suspended from his parents so he could have the house to himself, but failed to realize that his parents would lock the front door if they thought he was at school.
* DinnerOrderFlub: Helga, trying to pass herself off as Arnold's French pen pal whilst in disguise and with a very rudimentary knowledge of French, attempts to make a order from the menu of a fancy French restaurant. It isn't until she's happily tucking into the dish that the waiter informs her that she's eating cow brain and eggs... [[ForeignQueasine which prompts a dart to the bathroom]]. Arnold played it safe with a steak and fries.
* DisabilitySuperpower: The blind guy in "Das Subway" had a really good sense of smell.
* DisappearingBox: Helga gets involved in the trick in "Magic Show", but decides to run away instead of staying behind the secret wall, thinking what life would be like without her. It leaves Arnold trying to bring her back many times with no avail.
* DisneyAcidSequence: Helga experiences a bizarre series of hallucinations after drinking an ([[PlaceboEffect alleged]]) anti-love potion in "Helga's Love Potion."
* DisproportionateRetribution: Curly's main schtick, besides (or in addition to) being completely AxCrazy. Him terrorizing the gang through a cemetery dressed as an undead murderess because he couldn't be the one to tell a story is one thing, and him barricading himself in the principal's office and laying siege to the school with dodgeballs because he couldn't be ball monitor is another, but ''[[MoralEventHorizon enacting an elaborate plot to get Eugene expelled from school simply because Eugene borrowed and chewed on his favorite pencil]]?'' That's just insane. And, "FREE THE ANIMALS!!!"
* DistractedByTheLuxury: Rhonda frequently prioritizes her attention toward the gifts her parents shower her with.
* DoggedNiceGuy: Arnold becomes a mild version after realizing that he's interested in Lila, only for Lila to continually clarify to him that she's realized that she doesn't ''like'' like him.
* DoingItForTheArt: InUniverse. Mr. Hyunh, who has an incredible country-western singing voice, only likes to play music for his friends and family as a way to relax, while perfectly happy to work his restaurant day job. When Arnold and Gerald try to make his famous, he's clearly not comfortable with it.
* DoubleStandardAbuseFemaleOnMale:
** Zig-zagged with Helga. While her bullying (of everyone, not just Arnold) is not treated as seriously as a male bully would be, it is still not portrayed as being ''okay'' by the show, pointing out repeatedly that it is a problem, and that what Helga is doing is not acceptable behaviour for anybody. '''Helga on the Couch''': Principal Wartz didn't seem to pay much attention to Helga punching Brainy, as usual, until Dr. Bliss informs him of this. It's possible that Wartz, like the students, had grown accustomed to it or the instances didn't get reported considering how Helga is.
** However, in one episode, Helga throws glue on Arnold, and Arnold snaps and throws paint on her. ''Arnold'' is the one who gets yelled at.
** Played straight with Arnold's grandparents when they were kids, where his grandmother would do the same (if not worse) to his grandfather.
*** There is an unfortunate amount of TruthInTelevision in how bullying is reacted to in schools in this show. Principal Wartz's non-reaction is ''normal'' for an American school administrator, and bullying (be it physical or verbal) is largely given a blind eye unless someone outside the school makes an issue of it. And Arnold being punished for throwing the paint is also an unfortunate norm: Anyone who lashes out at a bully gets punished for "perpetuating the problem", [[KarmaHoudini frequently while the bully escapes with either a warning or no punishment at all.]]
* DownerEnding:
** "Arnold Betrays Iggy" ends with Arnold cutting off ties with Iggy after suffering public humiliation.
** "New Bully on the Block" ends with the gang being beaten up and losing Gerald Field to Wolfgang and Ludwig.
** "Operation Ruthless" and "Love and Cheese" have a downer ending for Helga. The episodes have the same basic plot, with Ruth and Lila, respectively. Helga brings it on herself both times, since she shouldn't be allowed to [[KarmaHoudini get away with what she does]], but both endings portray her as so ''pitiful'' that you can't help but feel for her.)
** "Helga and the Nanny" ends with Helga's home life going back to its dysfunctional state after she pushed away the one person that was improving it. Just like the above example, Helga doesn't really ''deserve'' a happy ending, but it's hard not to feel sorry for her.
* DreamSequence: Many dream sequences appeared in the first season when Arnold was portrayed more as a {{Cloudcuckoolander}}, but went away as the show went on.
* DrillSergeantNasty:
** Lieutenant Major Goose can be pretty petulant and demanding, he was Arnold's teacher for short time,(after Miss Slovak and before Mr. Simmons), he's a satire of Major Payne.
** Coach Wittenburg also had the sports discipline of a drill sergeant.
* DroppedGlasses: Happens to Phoebe in the hallway in "Hall Monitor", where she frantically searches for her dropped glasses as other students step on them.
* DuckSeasonRabbitSeason: Helga pulls this trick on Arnold in his dream in "Married", tricking him into saying he does want to marry her by switching sides of their argument after it's gone on long enough.
* DuringTheWar: [[http://www.dailymotion.com/video/x29x7hm_grandpa-phil-gives-hitler-a-wedgie_fun Grandpa's war story.]] Which includes the tale that he personally beat up Hitler, and this tidbit:
--> '''Arnold''': Grandpa, you did not fight Adolf Hitler! You're making this all up.
--> '''Grandpa''': Okay, ya got me. I made that part up. It was Goebbels.
* DysfunctionalFamily: Dear God, the Patakis. Very much so.
** We got Big Bob, the biggest {{Jerkass}} dad you'll see without actually perpetuating violence.
** Miriam, who is obviously an alcoholic based on her behavior, though the episode where she took over for Bob's beeper store shows that she has the potential to be somebody if not for her husband.
** Both whom [[ParentalFavoritism favor]] Olga, a bubbly [[TheAce straight-A receiving college student]] who [[StepfordSmiler doesn't acknowledge any of the family's problems]] and would rather not have any of her parents' attention.
** Helga, who can't stand any of it and [[ButtMonkey suffers from it all]].
[[/folder]]

[[folder:E]]
* EarlyBirdCameo:
** Monkeyman can be seen (and heard) in the background in several episodes before his Season 4 debut. In fact, he appears in the very first episode "Downtown as Fruits".
** Patty first appeared in "Ms. Perfect" as a nameless character who unintentionally falls victim to pranks Helga intended to inflict on Lila.
* EarlyInstallmentWeirdness:
** The original StopMotion shorts are nothing like the main series. Aside from being in a different animation medium, the shorts focus not on solving real-life problems, but on [[DreamSequence drifting off into Arnold's imagination]]. In addition, Arnold himself is a cross between MrImagination and a CloudCuckooLander, his fascination with [[EverythingsBetterWithDinosaurs dinosaurs]] is much more apparent, and the sequences themselves are [[MindScrew bizzare]] in comparison to the main series.
** The first season is a lot different from the other seasons. The animation is of much lower quality, with lots of OffModel scenes, there were fewer episodes centered on Helga (and she lacked any redeeming qualities for a while, with the abuse and neglect she suffered being used as a form of ComedicSociopathy), Arnold has a crush on Ruth, who is nowhere to be found after season 1, there is a heavier focus on bizarre one-shot characters as opposed to Arnold’s classmates, and on top of all that, Arnold is FAR more child-like and immature compared to the later seasons.
*** One early episode has Gerald as the voice of reason, and another has ''Pookie'' act as the voice of reason. Watching the later episodes you'd be surprised to see ''this''.
** The original pilot episode of the series depicted most of the characters as having differently-colored clothes and gave Gerald a more saturated skin tone.
* EasyAmnesia: Helga gets amnesia in "Beaned" after getting hit with a baseball. Subverted in that she gets her memory back normally when she wakes up the next day, not by getting hit again. However, she continues to [[FakingAmnesia fake amnesia]] to take advantage of Arnold's kindness, and when she feels guilty about it, she ''intentionally'' hits her head again so she can pretend that she just then got her memory back.
* ElectionDayEpisode: "Mr. Green Runs" had Marty Green, a butcher shop owner, angry at the fact that his councilman was failing to do things to help the community he represented (such as failing to get funds to repair and repave roads which had massive potholes) and spent more time golfing than working on legislation, decided to oppose him in the upcoming election. [[spoiler: Green wins]].
* EmbarrassingFirstName: Curly's real first name is Thaddeus.
* EnsembleCast:
** While Arnold is the kid with his name on the show's title, the series doesn't focus only on him. There's a certain (and rather large) group of characters that appear pretty darn often: [[{{Deuteragonist}} Helga]], Harold, Gerald, Phoebe, Sid, Rhonda, Stinky, Eugene, Mr. Simmons, Big Bob, Miriam, Grandpa, Grandma, Oskar, Ernie, and Mr. Hyunh.
** Then there's characters that appear fairly often, but not quite enough to be considered part of the main circle: Principal Wartz, Curly, Lila, Brainy, Suzie, and Olga
* EscapedAnimalRampage: In "Cool Party", Curly goes crazy (again) after he's among those not invited to Rhonda's party, and acting on an impulse, frees all the animals from the zoo.
* EvenEvilHasStandards:
** Big Bob's greedy, but he's not a murderer. He also refuses to bulldoze a tree upon realizing there were kids up there, but mostly ''his'' kid (which in of itself ''is'' something, considering how neglectful he usually is of Helga.)
** Helga gives Arnold a lot of crap but during the parents day episode when Bob calls Arnold (who was in earshot) an orphan, she is shocked and later goes up to Arnold and apologizes for it, justified because it's probably one of the only things that can hurt him.
** Played with when Rhonda (forced by circumstance to pretend to be his girlfriend) publicly dumps Curly and humiliates him, Helga is disgusted with her and tells her she has a black heart. To Rhonda, Helga is the biggest Jerkass around (only the audience knows about her hidden heart of gold).
** Speaking of Helga, the other children aren't really evil but can be [[KidsAreCruel cruel]] {{Jerkass}}es at times but even [[WhatTheHellHero they called Helga out]] when she framed her nanny for theft.
* EverybodyCries:
** "Ms. Perfect" involves Lila refusing to attend school after being the victim of a prank courtesy of Helga, Phoebe, Rhonda, Nadine, and Sheena. When the girls arrive at Lila's house to drop off her homework, they discover that Lila and her father are suffering from financial issues. The moment Lila's father breaks down crying when he is told he has been rejected as a job candidate, Helga and the other girls are remorseful over their treatment of Lila and [[TearsOfRemorse start shedding tears too]].
** In "School Play", when P.S. 118's production of "Romeo & Juliet" comes to a close, there is hardly a dry eye from anyone who had watched the play.
** In "Full Moon", Harold, Sid, and Stinky are all crying as they confess to Principal Wartz to mooning him in order to clear Arnold's name.
** In "Synchronized Swimming", Coach Wittenburg talks about his emotional experience watching a movie called "Come Back, Wayne", particularly the ending. By the time he has finished talking about his experience to his synchronized swimming team, he and most of his team are in tears. The only ones who don't cry are Arnold and Gerald, although Gerald's lips do quiver at one point.
** "On the Lam" has Harold, Sid, and Stinky once again crying together. Only this time, not only does it involve them thinking they blew up a police station, but they all cry twice in one episode! The first time is when they confess to Arnold about their "actions" in his basement and the second time is when they confess to everybody on live TV near the end.
* EveryoneCallsHimBarkeep: Stoop Kid, Chocolate Boy, Pigeon Man, Monkey Man, and The Jolly-Olly Man are just some characters on the show who are seldom addressed by their real names, if their real names are known at all.
* EveryoneLovesBlondes: Helga and Lila for Arnold to a certain degree, since he has blond hair and they are attracted to him (the latter at least initially).
* EveryoneWentToSchoolTogether: In this case, they all went to pre-school together, as revealed in a flashback in "Helga on the Couch." Strangely, even Harold was there, even though a previous episode had made Harold several years older than his classmates.
* EverythingsBetterWithRainbows: When Mr. Simmons becomes principal, there are a lot of rainbows at the school.
* EverytownAmerica: Hillwood is your typical made-up American city used as the setting for a work of fiction.
* EvilLaugh: Curly wins in the best psychotically evil laugh department, but Helga has a pretty impressive one as well. Some of the other characters get one in certain episodes: Sid for example gets on in "''Sid's Revenge,''" and [[BewareTheNiceOnes Phoebe]] gets a brief but creepy evil chuckle in "''Phoebe Breaks a Leg.''"
* EvilOverlooker: Scheck is depicted as a giant reaching for Arnold and friends below him in the poster for TheMovie.
* EvilPlan: Helga refers to her schemes to get what she wants as "evil plans", often with episodes dedicated solely to her pulling a series of them. A running gag in the series is that her evil plans always fail in ways that only help the person she's trying to hurt and hurt her instead.
* ExcitedShowTitle: ''Hey Arnold!'' is written as if it's something being shouted.
* ExpressiveHair: Helga's pigtails will occasionally perk up or droop depending on her mood.
* {{Expy}}:
** Lieutenant Major Goose from ''New Teacher'' is an expy of the title character of ''Film/MajorPayne''.
** Wally the Alligator in "Ransom" is the most obvious [[Series/BarneyAndFriends Barney]] expy ever.
** The mechanic in "Road Trip" is [[Film/SlingBlade Karl Childers]] with a unibrow.
* ExtremeDoormat:
** Phoebe takes everything Helga throws at her - however, she gets some CharacterDevelopment, in a few episodes where it's shown Helga ''also'' depends on Phoebe's support.
** Arnold himself lets people take him for granted a few times.
[[/folder]]

[[folder:F]]
* FailureIsTheOnlyOption: Helga's attempts at admitting her love to Arnold always end in failure. Ultimately subverted in TheMovie, when she finally tells him face-to-face.
* FanDisservice:
** In TheMovie, it's Grandma Gertie in her showgirl outfit. It comes with noticeable, unflattering cleavage and JigglePhysics. It gets weird when she's initially seen in it as she appears to have the body of a younger woman. Thankfully after she's arrested we just see her in a standard prison jumpsuit.
** Another notable instant is when Gertie decides to go naked in "Summer Love" after encountering some naturists at the beach, her nudity thankfully obscured by [[HandOrObjectUnderwear a surfboard]]. Phil even lampshades it.
-->'''Phil''': Aw, Pookie. Nobody wants to see ''that''!
* FandomSpecificPlot:
** "Jungle Movie" fanfics, write-ups, and speculatory scenes are very popular. Especially since "The Jungle Movie" was the imminent GrandFinale of the series.
** Fanfic writers are also particularly fond of the plot where a character leaves/runs away from town, stays away for years, and then comes back as an adult. This type of story usually stars Helga, who comes back [[ShesAllGrownUp hot]] and much nicer, and at the end finally manages to be with Arnold)
** It's almost difficult to find an Arnold/Helga fanfic that ''doesn't'' feature Arnold seeing Helga with her hair down and realizing she was "Cecile".
* FantasyHelmetEnforcement: The kids always wear helmets and other protective gear when they go biking.
* FatBastard:
** Harold is obese and was quite mean in the earlier episodes. As the series went on, he became TheBigGuy with a slight hint of {{Jerkass}}.
** Big Bob is slightly overweight and not a very pleasant guy at all.
* FatIdiot: Harold is shown to possess the IQ of a piece of furniture. This quote from Helga perfectly sums up why.
-->'''Helga''': Everything that happened today was your fault. You can't do anything right! Take the bus for example. Why do you think we missed it, Harold? Oh, let's see, hmm... maybe was it be because you were too busy eating twice your body weight in chocolate Num-nums?! Oh, how about this one? "Let's take the subway, I think it goes to Lincoln." Oh wait, no it doesn't, it goes straight to the bowels of the underworld!! Population: [[PunctuatedForEmphasis Homicidal! Toothless! Midget clowns!!]] "I know, let's steal their bike, they won't mind." Now, you'd think that would be enough to fill any moron's day, but you're not just any moron, are you, Harold? You're the king! Your day's just getting started! So, because of your amazing curiosity about the world around us, [[TooDumbToLive you pulled the plug out of the bottom of our getaway boat!!!]] You idiot.
* FireBreathingDiner: "Chocolate Boy" has Chocolate Boy exhale flames when he and Arnold try chili peppers as a substitute for chocolate to cure his addiction to chocolate.
* FirstNameBasis: Helga refers to her mother and father as "Miriam" and "Bob" respectively, most likely because she doesn't view them as true parents, [[ParentalNeglect and for good reason]].
* FeudEpisode: "Best Friends" focused on a temporary falling out between both Arnold and Gerald and Dino Spumoni and his songwriting partner Don Reynolds.
* {{Flanderization}}:
** Arnold started out as a good-natured kid that sometimes made mistakes, but as the seasons went on, he turned into an [[IncorruptiblePurePureness incorruptible, squeaky clean, advice-giving saint]].
*** This spread to other characters who contrast it - in later seasons they were practically total buffoons or borderline immoral jerks, watching some episodes in which the voice of reason is someone like Gerald or even ''Grandma'' seems rather weird.
** Eugene's bad luck intensifies with each passing season.
** Grandma started out eccentric and a little batty, but ultimately sane and always willing to give Arnold a little advice (even if it was delivered in a non-traditional manner), but she got slowly crazier as the series wore on and by the end of the series she's little more than a crazy old lady who lives in Arnold's house. This can be somewhat justified in a somewhat horrifying way - senility.
** Olga started out as overachieving drama queen that would ''actually be treated like Helga if she wasn't successful and understood Helga's plight'' to.... just a content, overachieving drama queen. Also, you'll be ''damned'' if you see Miriam functioning despite drinking and scouring the city to get Helga a sold out gift for Christmas in any later season.
** Lila started as a seemingly perfect yet struggling girl who had HiddenDepths, and finished as a ParodySue who was [[VerbalTic ever-so-certain]] about everything.
* FourTemperamentEnsemble: Arnold (phlegmatic), Helga (choleric), Gerald (sanguine), and Phoebe (melancholic/leuquine).
* FreeRangeChildren: The nine-year old cast runs about the city (which is quite big, mind) with little concern from any of their parents. This includes playing sports in the middle of a busy street, running away when a car comes. This particular instance doubles as TruthInTelevision.
* FreezeFrameBonus: If you pause in "Phoebe's Little Problem", you can see that apparently they have school over the summer. Maybe they're making up the days they missed from the Teacher's Strike?
* TheFriendNobodyLikes: Helga, due to her bullying tendencies, isn't well-liked by the other kids. Only Phoebe and [[DependingOnTheWriter occasionally]] Arnold truly consider her a friend. Everyone else just tolerates her out of fear and[=/=]or proximity.
* FreudianExcuse:
** As seen in one of Helga's [[ADayInTheLimelight days in the limelight]], "Helga on the Couch." She discusses with the school psychiatrist her obsession of Arnold which is deeply embedded into her [[DysfunctionalFamily family life]]. [[spoiler: On her first day of pre-school her parents were more focused on her sister [[ParentalFavoritism Olga]] playing the piano. They didn't even acknowledge her existence when she asked them to take her. She had to walk there herself and on the way it began to rain, mud got splashed on her, and a rottweiler stole her lunch. [[CrowningMomentOfHeartwarming Then Arnold gave her his umbrella, which was possibly the first time somebody showed her genuine kindness]]. She began her assertive personality when Harold stole her crackers and the other kids teased her about her crush. She explained to the psychiatrist that she treats Arnold the way she does because she fears rejection like how her family seemingly rejected her]]. It's safe to say that not one member of the audience had a [[TearJerker dry eye]] when the episode was over. And Helga was placed top of the show's [[TheWoobie Woobie]] list.
** Parodied with the Jolly Olly Man: If you had to drive daily to a wasteland of a city to sell ice cream to horrible children you will be a little crazy too (even more scary, the true source of his problems is his father, who doesn't believe in him and is clearly expecting him to fail).
* FrothyMugsOfWater: Miriam is hinted to be alcoholic in a way that doesn't mention alcohol. She's shown drinking "Smoothies" and falling asleep in odd places, as well as putting Tabasco Sauce in them. She has slurred speech and signs of depression.
** Averted in "Buses, Bikes, and Subways" when Mr. Simmons' class sings the "explicit" version of "99 Bottles of Beer on the Wall."
* FunnyForeigner: Mr. Hyunh has shades of being foreign comic relief at times, but Oskar Kokoshka defines this trope.
[[/folder]]

[[folder:G]]
* GagNose: Sid, Stinky, Oskar, and Grandpa all have big noses.
--> '''Sid:''' I bet [Rhonda] thinks I'm a geek because of my big nose!
--> '''Stinky:''' It's not ''that'' big.
--> '''Sid:''' Thanks, but you're only saying that because you have the biggest honker in the world. No offense.
--> '''Stinky:''' None taken.
* GainaxEnding: "Sid the Vampire Slayer". Throughout the episode, Sid believes that Stinky is a vampire, citing strange though incriminating reasons and even trying to take a stake to Stinky's chest. Fortunately, Arnold proves to Sid that Stinky is not a vampire...only to show at the very end [[spoiler: that Sid ''[[TheCuckoolanderWasRight was right]]'', as Stinky has a chat with a bat, reveals his sharp fangs, and cackles maniacally.]] This wasn't brought up again, so RuleOfFunny was probably in effect.
* On the other hand. The fact that the episode in question was the final season we'd never know for sure it this recent development would go beyond that episode.
* GayParee: Subverted. When Helga tried to pass herself off as Arnold's pen pal, he asked about her home and Helga responded that Paris is a big noisy city, [[CaptainObvious full of French people]]. Then Arnold recalled Cecile saying that she lived in a farm, catching Helga off guard.
* GentleGiant: Patty Smith the HugeSchoolgirl of P.S. 118 is reasonable and good-natured when she isn't bullied or provoked.
* GettingCrapPastTheRadar: [[Radar/HeyArnold Has its own page.]]
* GilliganCut: It's a RunningGag to immediately cut to characters doing what they said they wouldn't.
--> '''Helga:''' I am not taking the subway! ''(cut)'' I can't believe I'm taking the subway!
--> '''Gerald:''' There's no way we're fishing in the swan boat! ''(cut)'' I can't believe we're fishing in the swan boat.
--> '''Arnold:''' We are not calling our go-kart the "[[{{Portmanteau}} Mauve Avenger]]". ''(cut)'' I cannot believe we called our go-kart the "Mauve Avenger".
--> '''Helga:''' Look, I am not going to in there and tell them the truth and end up washing dishes. ''(cut)'' I can't believe I told them the truth and I wound up washing dishes.
--> '''Oskar''': I never lose! ''(cut)'' I can't believe I lost.
--> '''Helga:''' I am not gonna be part of your dumb little football game. ''(gets the shit beaten out of her)'' I can't believe I'm part of their dumb little football game.
--> '''Rhonda''': There is no way I am wearing that shirt! ''(cut)'' I cannot believe I am wearing this shirt.
* GirlyGirlWithATomboyStreak: Rhonda is a spoiled, rich Alpha Bitch, but she's not above playing football and baseball with her friends.
* GirlyScream: Sid, Eugene, and Mr. Simmons have feminine-sounding screams.
* GlassesGirl: Phoebe wears glasses.
* {{God}}: Appears in Stinky's prophetic dream in "Stinky's Pumpkin", voiced by Creator/TonyJay
* GonkyFemme: Patty was at first a girl that was tall and big enough to beat the official bully, Helga, and no characterization was given apart from being scary, strong... and wearing a skirt and a headband. In a later episode she has her own day in the limelight, where she is shown to be [[HiddenDepths feminine, polite and graceful enough to excel in Manner Classes]], even getting to tutor the shows [[GirlyGirl girliest girl]], Rhonda.
* GoodParents: Surprisingly, most of the cast members, except Arnold and Helga, have parents who do their best to raise them right. Some kids are shown only with one parent, but it's generally assumed the other one is there and simply not relevant to the plot.
* GrandFinale: Since ''The Jungle Movie'' was greenlit for 2017, it will serve as the final conclusion to the series, bringing an end to Arnold's journey in finding his lost parents. Though WordOfGod [[https://www.polygon.com/2017/10/6/16438576/hey-arnold-the-jungle-movie-new-season-episodes-nycc-2017 has stated]] that [[SeriesFauxnale a new season might be in the cards]] if the film does well enough.
* GranolaGirl: Is Helga's nickname for Sheena, which seems to be more or less accurate given her obsession with eating healthy.
* GRatedDrug:
** Chocolate Boy's obsession with chocolate is ''very'' similar to a drug addiction. In one episode, he begs Arnold to help him get over this. It is revealed that [[spoiler: his nanny who took care of him as a very young child always gave him chocolate. He was devastated when [[TearJerker she was forced to leave him.]] He ate chocolate to remind him of the one person who ever loved him.]]
** Miriam's [[FrothyMugsOfWater "Smoothies"]] are a clear way of hinting she's an alcoholic without having to mention alcohol.
* GroinAttack:
** Arnold accidentally hits Grandpa in the groin in "Mugged" when he tried to kick a can off his head.
** Played straight when Arnold and Gerald try to slip past two security officers working for Scheck in [[BigDamnMovie the movie]] and Gerald gives one of them a kick to the family jewels.
* GrumpyOldMan: Grandpa Phil is reasonable for the most part, but he does show a grouchy side whenever he argues with the tenants at the boarding house.
[[/folder]]

[[folder:H]]
* HalloweenEpisode: "Arnold's Halloween" was a WholePlotReference to Creator/OrsonWelles' ''Radio/TheWarOfTheWorlds'' radio prank.
* HatesBeingTouched: Helga doesn't like being touched by Arnold, or at least she pretends to.
* HateSink:
** It's probably not a coincidence that Wolfgang was introduced around the same time that Helga and Harold started undergoing their CharacterDevelopment. He's a worse bully than both of them ever were and has no redeeming qualities, so it's very easy for fans to hate him.
** There are also numerous one-shot characters that are this. In particular, Arnold, Oskar, Ernie, and Mr. Hyunh's rival Chauncey from "The Racing Mule" is a real piece of work. There is literally not a moment where Chauncey isn't arrogantly rubbing his victories in the heroes' faces, making fun of their mule Glueboy, and acting like an immature ManChild (including taunting Arnold and sticking his tongue out at Arnold like a six-year-old before the race). He even cheats by [[KickTheDog kicking Glueboy in the face]] during the mule race itself. Needless to say, he's such a detestable character that it'll be immensely satisfying to see Chauncey get knocked off his high horse (er, mule) when Arnold manages to beat him at the mule race despite Chauncey's efforts, which is immediately followed by SoreLoser Chauncey being kicked out of sight by his own mule.
* HeadlessHorseman: The Headless Cabbie is a legend surrounding a cabbie being decapitated and his ghost haunting the park at night.
* HereWeGoAgain: Several episodes end with the characters going through similar events to the ones they just resolved, like "Weighing Harold" (where Harold is again given a bet that he can't eat 50 Mr. Fudgie bars in one sitting) and "Phoebe Breaks a Leg" (where this time, Helga is the one with a fractured leg and Phoebe is the one who has to tend to her needs until she heals).
* HeroesWantRedheads: Arnold is attracted to the red-headed Lila.
* HeterosexualLifePartners: There are more than a few close friends consisting of two people of the same gender.
** Arnold and Gerald.
** Principal Wartz and Mr. Simmons, at least during the "karaoke night" ending of "Principal Simmons." (Played with, as according to the series creator Mr. Simmons is actually gay.)
** Helga and Phoebe, appropriately enough, considering their respective relationships with Arnold and Gerald.
* HeWhoMustNotBeSeen: Gerald's informant "Fuzzy Slippers" was mentioned several times in the early episodes, but was never actually seen.
* HiddenDepths: As confirmed by [[AllThereInTheManual The book six of the series Hey Arnold!]] [[http://www.amazon.com/Arnold-Arnolds-Files-Groening-Bartlett/dp/0439381495/ref=pd_sim_b_3 Arnold's E-Files]] Brainy is as eloquent as Helga… only that he cannot talk because his asthma.
* {{Hikikomori}}:
** Stoop Kid somehow manages to be both pathologically afraid of leaving his home and a gutterpunk at once.
** Arnold becomes this when he loses his hat in "Arnold's Hat", saying that he'll never come out of the house without it.
* HitFlash: The show had an instance of this, featuring colorful stars rapidly flying on a black background that originated in the pilot episode, and was [[StockFootage recycled numerous times]] throughout the series and even in the movie.
* HollywoodVoodoo: In "Sid's Revenge", Principal Wartz gives Sid detention for a prank he didn't pull. Out of revenge and his frantic paranoia, Sid carves Wartz' likeness into a bar of soap. The next day, Sid finds out that Wartz is in the hospital, and is told by the doctor that he's already "[[LiteralGenie checked out]]." Following this is a string of signs that soap voodoo worked. HilarityEnsues.
* {{Homage}}: 'What's Opera, Arnold?' was a {{Homage}} to the opera ''Carmen'', right down to altered song lyrics. It's also an homage to the WesternAnimation/BugsBunny cartoon, "WesternAnimation/WhatsOperaDoc?"
* HomelessPigeonPerson: A "pigeon man" (trope picture) lives on a rooftop, with some elaborate cages containing hundreds of pigeons. At the end of the episode, he actually flies away carried by his birds.
* HonorBeforeReason: Almost every episode is about Arnold choosing to do the honorable thing over the logical thing.
* HotTeacher:
** Arnold finds substitute teacher Ms. Felter attractive in "Crush on Teacher".
** Olga is seen as attractive by the male students in "Student Teacher".
* HourglassPlot:
** Happens to Phoebe and Helga in "Phoebe Breaks A Leg" - when Helga is indirectly responsible for Phoebe getting injured, out of guilt she starts waiting on her in the way she often had Phoebe wait on her. In a twist, Phoebe quickly realizes this is happening and - tired of being treated like an assistant all the time - [[BewareTheNiceOnes conspires to keep it that way for as long as she can.]]
** Happens to Arnold and Iggy in "Arnold betrays Iggy" - For accidentally blabbing an embarrassing secret of his friend Iggy, Arnold unsuccessfully tries to apologize to him. When Iggy finds out the truth, he begs Arnold for his forgiveness.
* HugeSchoolgirl: Big Patty is way bigger than the other students. Also Sheena, who's as tall as most of the ''adults'' on the show.
* HumiliationConga: Helga tends to get these in episodes where her evil schemes go south in particularly unpleasant ways. Rhonda, as well, gets pretty severe ones in episodes where she's particularly [[BreakTheHaughty haughty]].
* HypocriticalHumor:
** In "Gerald's Tonsils" Gerald tries to practice singing with with his new post-tonsillectomy voice and a kid overhears him and makes fun of it, saying he has a "crazy voice." The kid has a very annoying and nasally voice himself.
** In "Helga's Masquerade" Harold makes fun of Helgs's BigOlUnibrow despite the fact that Harold has a unibrow too.
** "Girl Trouble" features this classic bit from Pookie.
--> '''Pookie''': Just remember, Arnold. Violence is not the answer.
--> ''She karate chops a watermelon to slice it, hard enough to splatter some of it across the wall.''
** "Spelling Bee" has a banner hung outside the location holding the titular spelling bee. What does it read? "WELCOME SPEELERS!"
[[/folder]]

[[folder:I]]
* ICantBelieveItsNotHeroin: In Chocolate Boy's self-titled episode, Arnold helps Chocolate Boy quit his "obsession" with chocolate for two weeks, only to get a 10 pound bag of chocolate which he immediately devours in one sitting. After Chocolate Boy realizes how pathetic he has become, he wants to quit for good. Chocolate Boy's mannerisms in this episode are very similar to a crackhead. Justified somewhat by the sheer quantity of chocolate Chocolate Boy consumes. Child or adult, that much caffeine and sugar will mess you up.
* IfIHadANickel:
-->'''Harold''': If I had a dime for every time somebody called me dumb...[[IResembleThatRemark I'd sure have a whole bunch of dimes!]]
* IgnoredConfession: In TheMovie. Helga says she loves Arnold. And then they agree it was heat of the moment.
* IKnowKarate:
** Arnold learns it in "Mugged." He ends up becoming an ArrogantKungFuGuy who ended up inadvertently chopping the clothes off of some guy who was looking for the bus stop.
** In the episode "Career Day," Helga comments that the ''jujutsu'' class she took really helped her when taking down the perps she encountered on her police "ride-along."
* ImOkay: the catchphrase of Eugune said when something bad happens to him.
* ImpossibleLeavening: When the kids try to bake the world's biggest pizza puff, the whole thing explodes after Sid mentions that when reading the amount of yeast to use, he [[{{Mismeasurement}} misread]] "tsp" as "[[EpicFail ten square pounds]]".
* IneffectualSympatheticVillain: Helga in episodes where she's antagonistic, particularly as the series goes on. Especially noticeable in episodes involving Lila. The series does this especially well: because we know Helga's true insecure reasons for doing what she does, when her {{Evil Plan}}s to humiliate Arnold or Lila or whoever's incited her jealous wrath fail epically and/or backfire hilariously on her the audience laughs, but also feels truly sorry for her.
* IneptAptitudeTest: The plot of "The Aptitude Test" has Helga and Harold's test results being mixed up and causing problems for both of them.
* InformedAttractiveness: Lila. Nearly every boy in Mr. Simmons' class has a crush on her (especially Arnold) and her beauty is often commented on by others. However, she doesn't look much different than the other girls, aside from the ones with exaggerated features such as Helga and Sheena.
* InformedDeformity: While it's clear that Helga probably won't be winning any beauty pageants anytime soon (though she was a model for a brief time) she is one of the few characters who is outright called ugly despite the fact that this world is full of football heads, unibrows, inhuman looking faces and whacky hairstyles.
* InkSuitActor:
** Mr. Simmons strongly resembles his voice actor, [[Series/{{Frasier}} Dan Butler]]. They're are also both gay.
** Councilman Gladhand in "Mr. Green Runs" looks a lot like his voice actor, John O'Hurley.
** Radio announcer Nashville Ned resembles creator Craig Bartlett.
** Mr. Scheck from the Movie looks a lot like his voice actor Paul Sorvino.
** Coach Wittenberg has a slight resemblance to Jim Belushi.
* IronicEchoCut: So very, very many times, coupled with the GilliganCut. "I can't believe I'm taking the subway."
* IronicInversion: Stinky had no intention of becoming the mascot for Yahoo Soda in "Stinky Goes Hollywood" and only intended to be at the auditions to cheer Arnold on, yet he ends up picked after everyone else who auditioned was rejected.
* IronicNickname: Curly, as Lieutenant Major Goose pointed out.
-->'''Lt. Major Goose''': [[LampshadeHanging YOUR HAIR'S NOT CURLY!]] WHAT'S YOUR REAL NAME?
-->'''Curly''': Thaddeus.
-->'''Lt. Major Goose''': *{{beat}}* CURLY, GO STAND OVER THERE!
* InsufferableGenius: Played straight with Phoebe. "Phoebe Cheats" and "Ms. Perfect" even shows us that she has to meet her own expectations with "being the best at everything".
* InsultBackfire:
** When the boys meet Rex Smythe-Higgins III in "Tour de Pond", Gerald mocks his haughty attitude by asking if he's the owner of the park. Rex tells him that his family actually ''does'' own the park.
** "Phoebe Skips" averts it, with the sixth-grade girls using Phoebe's intelligence and niceness to their advantage.
* IrrevocableMessage: Helga got high off of laughing gas in "Helga Blabs it All" and left a message on Arnold's answering machine declaring her love for him, then spent the rest of the episode trying to delete it.
* ItsAllMyFault: Arnold in "Beaned" and "April Fool's Day" blames himself for Helga's amnesia and temporary blindness in both episodes; Helga in "Phoebe Breaks a Leg" is shown to be very remorseful for Phoebe breaking her leg while doing errands for her.
* IWantMyBelovedToBeHappy: Craig Bartlett says that Brainy ultimately wants Helga to be happy and wouldn't mind if her happiness meant not getting together with her.
* IWasBeatenByAGirl: Harold by Big Patty in an arm wrestling match in "Harold vs. Patty". He is so upset, he attempts to escape from those mocking him by hiding under a drinking fountain. He finally gets over it by the end of the episode - after she beats him again in the citywide arm-wrestling championships - and smacks Sid and Stinky together when they [[TrashTalk trash talk about him]] after his loss, but not before publicly defending Patty as the better opponent. (The end of the episode implies a RelationshipUpgrade for Harold and Patty due to this.)
* IWishedYouWereDead: Sid with Principal Wartz in "Sid's Revenge". When Principal Wartz goes missing after Sid carves a voodoo doll of him out of soap, Sid comes to the conclusion that his actions have resulted in Wartz' death and is very distraught by his assumption that he killed Principal Wartz.
[[/folder]]

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