Because of the show's longevity, many characters have appeared throughout the show, each with a wide array of personalities and other character traits. The following describes characters from the picture books and animated television series by Marc Brown:


[[folder:Common character tropes]]
* BookDumb: Depending on the writer, any one of Arthur's immediate friends (except Brain), Arthur himself, or even the grown ups may be subject to this.
* {{Bookworm}}: Every child character in the show has been seen in the library at least once.
* ButNotTooForeign: Do any of the characters [[AmbiguouslyBrown appear to be their ethnicities or nationalities]]? Then again, they are anthropomorphic animals...[[FurryConfusion Or are they?]]
* CartoonCreature: One of the commonly asked questions about the show is the subject of which animal some of the characters are. Arthur and his family are the most confusing since they do not look like aardvarks at all. Prunella is another character that's debated upon; it is undecided on whether or not she is a poodle or a rat. PBS says she's a rat but Marc Brown says she's a poodle.
* CloseKnitCommunity: Some episodes imply that the parents in Mr. Ratburn's class have all shared contact information with each other, while others make it clear that some of the parents are on a FirstNameBasis.
* FreeRangeChildren: Arthur and co. are about only eight years old and are in third grade, yet they run all about Elwood City much like teens several years older. None of their parents seem to be concerned, with the exception of what happens in S2's "Lost!" where Arthur accidentally rides the bus line to the city limits. PlayedWith in an episode where for some reason, Brain and Binky think they're trapped at the soccer field and their moms forgot to pick them up. They go everywhere else in their neighborhood, but can't walk home?
* GoodParents: All of the parents can count. What's interesting is that there are a rather startling number of examples of Arthur and D.W.'s parents not doing their job right (although when you consider the current length of the show, it's not entirely unexpected).
* IdiotBall: In later seasons especially, long-running characters are depicted doing dumb things, even though they know better, or in some cases, [[AesopAmnesia have been shown to learn better]].
* ItsTheBestWhateverEver: Many of the show's characters have webpages detailing such experiences.
* LimitedWardrobe The characters all have characteristic outfits by which they are identified. Depending on the episode or the setting, they may be changed.
* LivingProp: There are a number of such characters in Arthur, mostly recurring townspeople and the students in D.W.'s class. Of important note are a pair of rabbit kids who've been in Arthur's class since the S1, but are not as developed as their classmates (in 20 seasons, the male one has only talked five times, and the female one doesn't speak at all until season 19, where she gets a single DayInTheLimelight episode, aptly named "Maria Speaks"). It was confirmed at New York Comic Con 2013 that the two rabbit kids are indeed named Alex and Maria, and that the possibility of becoming Ascended Extras is open.
* NotAllowedToGrowUp: Even though some characters have birthdays over the course of the show, the characters are shown to never physically age, outside of occasional flash-forward or fantasy. Lampshaded by D.W. in S1's "Arthur's New Year's Eve", suggesting that she's trapped in some kind of time warp that causes her to never get any older.
* PunnyName: Most characters. The Crosswire family is probably the most obvious.
* RenaissanceMan: Most of the kids in Arthur's class play a sport and an instrument, and love to read. Even George, who struggles in these areas and starts off being shy and socially awkward, finds his stride as a carpenter and sports commentator.
* RoundedCharacter: One of the top reasons for the show's success.
* RotatingProtagonist: This is how things work, so different members of the cast get their own EpisodeTitleCard.
* TrademarkFavoriteFood:
** Very subtle, but just about EVERYONE on this show likes snacking on popcorn.
** There's a trademark favorite drink, at least in earlier seasons anyway, for the Read family. They are almost always seen drinking milk at meals.
* WiseBeyondTheirYears: A number of characters, from D.W.'s friend Emily to Arthur and his friends. They're not your average third-grade kids, after all. One of the best examples is D.W. and her zany BatmanGambit to trick Arthur and The Brain to take her to the science exhibit in S4's "Prove It!", ''and it worked.''
* ZanyScheme: Lampshaded by Arthur in "D.W. and Bud's Higher Purpose." During the intro, he explains D.W.'s propensity for this has gotten worse since she met Bud.

!3rd/4th grade cast
[[folder: Arthur Timothy Read]]
-->'''Voiced by:''' Michael Yarmush (seasons 15), Justin Bradley (season 6), Mark Rendall (season 6 re-dub; seasons 7-8), Cameron Ansell (seasons 9-11), Dallas Jokic (seasons 12-15), Drew Adkins (seasons 16-17), William Healy (seasons 18-19), Jacob Ursomarzo (seasons 20-present)

The title character of the show. He and his family members are aardvarks, though it is not obvious due to the lack of elongated nostrils.
* {{Adorkable}}: For a third grader, anyway.
* ArtEvolution: Applies to the book version, where he starts out as an actual aardvark (looking more like an anteater), and would slowly change in design until he came to his current look.
* AdultFear: Has a moment of this in-universe when he and his friends suspect they brought home a venomous snake. [[spoiler:It's actually not.]]
* BerserkButton:
** Do not mess with his model planes. [[LaserGuidedKarma D.W. learned this]] [[KickTheSonOfABitch one the hard way]].
** NEVER make fun of his glasses. Just ask Binky.
* BewareTheNiceOnes: Normally a good-natured NiceGuy, but it's ''not'' a good idea to anger him. When D.W. destroyed his model plane and chose to blame him instead of apologising for her actions, he ''erupted''.
* BigBrotherBully: To D.W. and Kate at times. Of course, he won't admit that though.
* BigEater: Has shown himself to be this at times, ''especially'' if cake is nearby.
* BigYes: When he finds out that Buster is coming home from a LongBusTrip with his father in S3's "Buster's Back".
--> *Answering the phone* Hello? Yeah. Yeah? '''YEAH!'''
* BlackBeadEyes: Whenever without his glasses. However in earlier seasons and in any scene of him when he was younger he is typically seen with realistically drawn eyes.
* ButtMonkey: Would become one in later seasons.
* CatsAreMean: Was a firm believer of this, as exemplified in "Francine and the Feline (S3)"; as of "D.W.'s Furry Freak-Out (S12)" however, he seems to not mind them anymore.
* CharacterBlog: The Arthur Facebook page.
* CharacterTics: Arthur fiddles with his glasses when he's lying.
* CrazyConsumption: D.W., when imagining Arthur in a negative light, sometimes has him digesting cake either in one bite or in a mess. In "D.W. Gets Lost" [[spoiler: this actually happens.]]
* CrowdChant: Arthur gets one when he is cleared for embezzlement in "Arthur Accused!"
* DeadpanSnarker:
--> '''DW:''' Where were you between six months ago and yesterday?
--> '''Arthur:''' Listening to you whine about the snowball 24 hours a day.
* EyeGlasses: Has these. Was formerly self-conscious about them, too.
* TheEveryman: In sharp contrast to a group of widely varied friends with telling character traits. Lampshaded in S6's "Best of the Nest", when Arthur settles on "Just Plain Goose." This is extremely poignant when one considers that most of the later season's episodes focus less on Arthur.
* EyeCam: Almost all of "You Are Arthur".
* {{Facepalm}}: A very brief one after [[DramaticDrop dropping the wedding ring]] in "D.W. Thinks Big".
* FullNameUltimatum: Unlike D.W., he has only ever been issued one once throughout the show in S4's "Arthur's Big Hit", and it is lampshaded.
-->'''Mrs. Read''': Arthur Timothy Read, come here!
-->'''Arthur''': [[OhCrap Uh-oh, middle name.]]
* FoolishSiblingResponsibleSibling: The Responsible to D.W.'s Foolish. [[ParentalFavoritism Not that Mr. and Mrs. Read seem to mind]].
* GameShowAppearance: Arthur winding up on in-universe ''Riddle Quest'' in S5's "Arthur and the Big Riddle".
* GuiltyPleasures: Arthur is secretly a fan of in-universe toddler's show "Love Ducks". He keeps it a secret because (per the title of the S4 episode) "That's a Baby Show."
* {{Headdesk}}:
** He is so exhausted from PanderingToTheBase in S1's "Arthur Writes a Story" that he does a Double Headdesk.
** He does it again in S8's "D.W., Dancing Queen", when he and his friends overhear D.W. tell everyone of his nightmares about his underwear, and even brought it to school for all to see.
* TheHero: As the title character and de facto leader of his friend group.
* HellBentForLeather: He wears a leather jacket in S20's "Buster's Second Chance" combined with a CoolShades version of his normal glasses, in an alternate timeline where he never befriended Buster and became a Tough Customer instead.
* HeterosexualLifePartners: With Buster.
* HumiliationConga: "Arthur's Big Hit" in a nutshell. After punching DW, he gets grounded, then all his friends get angry with him for what he did. Afterwards, he gets punched out by Binky only to get not much sympathy from his parents.
* HypocriticalHumor: He accuses his friends of "not being able to stand a little competition" when playing games with them in "Arthur the Loser". In this episode he resorts to cheating against all of his friends because he proved to be a SoreLoser before his scheme was uncovered.
* IdiotBall:
** "So Funny I Forgot to Laugh" represents such a moment of weakness for Arthur that it's unconvincing.
** Arthur's cost-cutting ideas in "Arthur Read Super Saver" are more likely to come from the four-year-old-cast, like bathing in water from the Molinas' sprinklers, or trying to cut his family's water bill by getting Pal to lick food stains off the flatware.
* JerkassBall:
** In "So Funny I Forgot To Laugh", wherein he repeatedly makes fun of Sue Ellen's sweater even after she told him to stop, and on top of that, he sent her a BackhandedApology letter. Thankfully, [[JerkassRealization he realizes that he was acting like a jerk]] when Sue Ellen tries to switch classes.
** He was particularly nasty to Francine when she introduced him to her new cat Nemo in "Francine and the Feline", and was convinced Nemo would hurt Pal when at the time they were just playing. He never apologized for this, and it seems he wouldn't completely let go of his prejudices towards cats until later seasons. .
* KidHero: Naturally, since he's a 3rd-grader and the main protagonist.
* KickTheSonOfABitch: Punching [[BrattyHalfPint DW]] in "Arthur's Big Hit".
* LaserGuidedKarma: Hit with his ''hard'' in "Arthur's Big Hit". In that episode, he punches out DW, but Arthur gets punched by Binky later on in that same episode. His parents lampshade it. "Now you know how DW feels."
* MeaningfulName: Arthur ''Read''. Appropriate, given his love of books.
* MusicalisInterruptus: The teaser for "That's a Baby Show!" has Arthur demanding a stopdown when Mary Moo Cow and co. randomly show up in his bedroom.
* NeverLiveItDown: An InUniverse example; Frequently accused by D.W. of having stolen her snowball without any evidence; also he still hasn't forgotten the incident where he split his pants, the latter being so much so that Muffy urged him to forget it and move on.
* NiceGuy: All faults aside, he is usually kind and sweet.
* OfficialCouple: He is shown married to Francine in the future on multiple occasions, despite massive denial between each other in S2's "Arthur and the Square Dance".
* PinocchioNose: Has an all-too-obvious habit of fiddling with his glasses when he lies.
* TemptingFate: In "Arthur Babysits", Arthur boasts that babysitting is the easiest job on earth, having to take care of both D.W. and Kate. Then comes the first time where he must babysit the ''Tibble Twins'', who he said "did't look so bad". And the rest is history.
* ThisLoserIsYou: Arthur could be described as this, DependingOnTheWriter.
* TheUnapologetic: A few times, such as in "Arthur's Big Hit" when he refuses to apologize to DW for punching her, and in "So Funny I Forgot to Laugh", where he writes a BackhandedApology letter to Sue Ellen for making fun of her sweater.
* WouldHitAGirl: If punching DW in "Arthur's Big Hit" when she broke his model plane is any indication.
* YoureInsane: Arthur to D.W. after the latter announces plans to live with Mary Moo Cow in S5's "The Last of Mary Moo Cow".

[[folder: Buster Baxter]]
-->'''Voiced by:''' Daniel Brochu, Robert Bell (Living Books)

Best friend of Arthur. He and his divorced parents are rabbits.
* AgainstMyReligion: In S7's "Buster's Amish Mismatch" when he became Amish after a field trip.
* AgentMulder: Firmly believes in the existence of aliens.
* AlliterativeName: '''B'''uster '''B'''axter.
* AmateurSleuth: One of Buster's trademarks, often imitating hard-boiled PrivateDetective stories when he's on a case.
* BadassBiker: Arthur imagines him as one if Buster was a teacher in S8's "D.W., Dancing Queen", complete with CoolShades, CoolBike, and a [[HellBentForLeather leather jacket]].
* BeCarefulWhatYouWishFor: The teaser for "Arthur's Substitute Teacher Trouble" ends with Buster wishing that Mr. Ratburn would disappear. In the aforementioned episode, when Mr. Ratburn loses his voice and has to go on sick day, his class ends up receiving substitute teachers that turn out to be worse at teaching than him.
* BigEater: So much so that during a fantasy sequence in S3's "I'd Rather Read it Myself", D.W. imagines him as a robot that only exists to eat. One wonders just how the kid can stay lean. Often leads to CrazyConsumption. This became a plot point in S16's "Too Much of a Good Thing", where Buster has to prove to Arthur he can control his eating habits when a special Girl Scout cookie goes on sale.
* BookDumb: Played with; Buster is used to getting F's in class, nearly getting held back a year for it. He has misspelled Arthur's name and once spelled "soccer" with two K's and a Q. However, it is shown in episodes such as "Buster Makes the Grade" that [[BrilliantButLazy Buster can get good marks when he fully applies himself]]. His insight outside of the classroom though is usually a case of DependingOnTheWriter.
* ClearMyName: "Arthur Accused!"
* {{Cloudcuckoolander}}: Extremely superstitious, and is very, VERY obsessed with extraterrestrial life.
* EarsAsHair: Buster's mother makes him wear an embarrassing shower cap when he goes swimming, but his ears are more prominent than most, and it would be dangerous to get water inside of them.
* EurekaMoment: How Buster usually solves his cases. "Overflowing?" "That song!"
* ExpressiveEars: They droop when Buster is upset. "Buster Makes the Grade" is a good episode to watch if you want to see him doing this several times.
* FailureIsTheOnlyOption: Often has this attitude towards his grades in school, being prone to poor marks due to his lack of focus. Usually PlayedForLaughs, but in "Buster Makes the Grade" when he risks repeating the third grade, it's treated as anything but.
* ForWantOfANail: S20's "Buster's Second Chance" reveals that had Buster never befriended Arthur as kids or failed the test that would have let him go a gifted school, Arthur would have met pre-HiddenDepths!Binky instead and become a [[{{Jerkass}} Tough Customer]] instead of the NiceGuy he is in the show.
* HeterosexualLifePartners: With Arthur.
* HypnoFool: In S11's "Buenas Noches, Vicita", one of D.W.'s friends (Vicita) can't go to sleep. D.W. tries several methods, including trying to get Buster to hypnotize her to sleep. A couple of seconds later...
* {{Hypocrite}}: In "The Blizzard" he mocks Francine for not finishing her report on the pioneers when she was supposed to, which forces her to redo it even as the blizzard rages across town. Yes, the kid who is known to put off his work to the last minute and struggles to keep his grades up thinks he can lecture Francine on this mistake, earning him a well-deserved snowball to the face.
* ItsAllAboutMe: In "Buster Baxter, Cat Saver", where the public's obsession with Buster's alleged "heroism" in rescuing a cat from a tree causes him to abuse his time in the limelight. He eventually got over it after the episode.
* {{Keet}}: He's the most energetic and funniest of Arthur's friends.
* TheLancer: A position shared with Francine, to contrast Arthur's TheHero.
* LittleKnownFacts: Buster will believe anything he reads on the internet, as shown in S9's "Buster the Myth Maker".
* MeaningfulName: Buster's street address is 7 Roswell Court. An alien spaceship is rumored to have crashed in Roswell, New Mexico.
* NotSoDifferent: With, of all characters, Mr. Ratburn. They seem opposites in most respects, especially in regards to anything school-related. Buster has a (rather silly) fear of his teacher's love for learning. Despite this, the characters share many other definitive personal tastes. The biggest examples? Both obsessively love desserts, both watch cartoons, and Mr. Ratburn seems to have been much more like Buster in his youth according to what was seen on an old videotape from his high school days.
* {{Nerd}}: His aforementioned obsession with extraterrestrial life.
* NeverMyFault: He's hit with this when he does a history report and intends to open it with a joke for the class, and is furious when Binky beats him to the punch after hearing the joke from Buster earlier. Buster receives a "D" on his report, and openly blames Binky for it until Arthur makes him realize that it's his own fault that he put no effort into the actual assignment.
* ThePigPen: Often shown to have poor hygiene; so much so that he was the only student at Lakewood Elementary not to be affected by an outbreak of head lice. Unfortunately, it is not unusual to see him eat stuff off the floor, neglect to wash himself, or display poor table manners.
* PutOnABus: S2's "Arthur's Faraway Friend" has Buster leave the show to travel the world with his airline pilot father, which starts the spin-off show "Postcards from Buster". [[TheBusCameBack He comes back]] at the start of S3.
* StrangerInAFamiliarLand: The main plot points of S3's "Buster's Back" and "The Ballad of Buster Baxter".
* TerrifiedOfGerms: Plot point of S11's "Germaphobia".
* UnwittingInstigatorOfDoom:
** Steals a Cyber Toy in "Nerves of Steal", stuffing it in Arthur's backpack and then must confess when guilt takes over. He not only gets Arthur in serious trouble when they get caught, but he is grounded an entire month with no dessert for his troubles.
** In one episode he becomes careless with a high-powered telescope he bought to observe the stars, and for this gets a reading suggesting that a comet would hit the earth, eventually causing a panic among his peers. Thankfully, everyone found that the telescope was just missing a piece.
* WildTake: In his nightmare in S1's "Arthur's First Sleepover".
* YourMom: Told Binky his mother eats gym shorts in one episode. [[BerserkButton Binky didn't take it too well.]]

[[folder: Francine Alice Frensky]]
-->'''Voiced by:''' Jodie Resther

2nd best friend of Arthur. She and her family are monkeys.
* AcademicAthlete: A mild case. In addition to being a PassionateSportsGirl, she generally makes pretty good grades; Mr. Ratburn has singled out her work as "superb" before, and she was one of Buster's main tutors in "Buster Hits the Books."
* AesopAmnesia: In early episodes she would frequently tease Arthur for her own amusement; In "Arthur Makes the Team" she apologizes for this habit to Arthur, only to tell him later that she gets to tease him again if he flunk basketball season.
* TheAce: Exceptionally good at almost every sport that exists, always has the last word with some witty or sarcastic reply, and is usually the one that ends up having to bail out one or all of her friends in some way or another. She might not be so good at badminton or skiing, if "The Good Sport" is any indication. Once she befriends Jenna, she will play badminton, but previously said it was "for wusses."
* AddedAlliterativeAppeal: A book in a bad dream that Francine has is entitled "Francine Frensky: Fraud!".
* AcquiredSituationalNarcissism: Happens in "Francine Frensky, Superstar," when Francine gets the lead in a school play.
* AlliterativeName: '''F'''rancine '''F'''rensky
* AmbiguouslyBrown: Many people pictured Francine and her family as being rather dark-skinned or even black, but considering that they're Polish Jews...
* ArtEvolution: In the first few books she wore dresses and her muzzle didn't blend into her face, making it more obvious she's a monkey.
* BerserkButton:
** Beating her in anything sports related.
** "A ''griffin''. A ''griffin''. A ''griffin''..." Note that this was in an ImagineSpot in S1's "Meek for a Week", showing what would happen if Francine kept her anger bottled up for too long.
** Insulting Hanukkah also qualifies, as seen in the Christmas special.
* BreakTheHaughty: Francine has needed a little attitude adjustment from time to time when she gets a little too abrasive.
* DeadpanSnarker: Has plenty of snark at her disposal.
* {{Determinator}}: Always pushes herself to be the best at what she does, and doesn't respond well when something slows her down.
* EatingLunchAlone: Muffy lets her take the heat for cheating on a math test in "Arthur and the True Francine". Francine is too despondent to sit with company.
* EstablishingCharacterMoment: The events described in the following entry take place in the second half of the first episode.
* FemininityFailure: Francine tries to be feminine for one day, picture day, where she goes to school in a dress and doesn't play kickball during recess so she'll be presentable for her photo. She ends up playing anyway, and being scruffy in the picture.
* FriendlyRivalry: With the Brain when it comes to sports, as the two are closely matched when it comes to their physical skill. Not always the case though, as seen in "The Big Blow-Up".
* HellIsThatNoise: Anytime Francine tries to sing and drum at the same time. It sounds more like she's just hollering, or as she puts it after (Unknowingly) hearing herself on tape, "an elephant crushing Mr. Ratburn's car".
* HeterosexualLifePartners: With Muffy.
* HollywoodToneDeaf: Subverted by the end of S4's "To Beat or Not to Beat"; she isn't a bad singer, she just can't sing and drum at the same time. Although in later seasons, she would become a much better singer, and her drumming would rarely if ever be mentioned or seen.
* HypocriticalHumor: Francine often criticizes other people for being mean, despite being a textbook example.
* InformedAbility: Supposedly she can cook, as seen in "Love Notes for Muffy"; This has rarely been showcased since.
* ItsAllAboutMe: Frequently guilty of this, especially when it comes to her sports.
* JerkJock: She gives off vibes of this.
* JerkWithAHeartOfGold: Depending on the writer, as there are plenty of episodes where Francine is not a jerk.
* TheLancer: Shared with Buster.
* NotSoDifferent: Turns out she doesn't like being teased either, as shown in the events of "Draw!" when everyone gives her a taste of her own medicine after she coldly insults Fern. Thankfully this is a habit she does a lot less in later seasons.
* OfficialCouple: She is shown married to Arthur in the future on multiple occasions, despite massive denial between each other in S2's "Arthur and the Square Dance". She insisted on doing the rescue scene in "Arthur Makes a Movie" and was keen to play spin the bottle at Arthur's birthday party, possibly in the hope of getting to kiss Arthur.
* OnlySaneMan: Occasionally fills this role, and is more often than not shown to have a good deal more common sense than some of the others.
* PassionateSportsGirl: Francine is very athletic and loves sports, especially soccer, football, kickball, and bowling. The only sports she doesn't excel at are badminton and figure skating (which she dismisses as "girly"). Francine is very determined, perhaps even restless, and if she doesn't have an immediate knack for a certain sport or skill, she can become frustrated.
* PrimaDonnaDirector: In S1's "Francine Frensky, Superstar".
* PlagiarismInFiction: Francine plagiarizes a school essay in "Francine's Pilfered Paper". While the full range of real-life consequences of plagiarism are discussed, Francine is only asked to repeat the assignment, and she ends up with a lower grade.
* SlobsVersusSnobs: Between her and Muffy.
* SoreLoser: One of her longtime trademarks; taken to new heights in "Arthur Calls It", where she berates Arthur for outing Buster in a baseball game in a play that was obscured to most observers and tries to discredit him, all because she was angry they had lost. Taken to an extreme in "The Good Sport", where she lost the Athlete of the Year Award to Jenna that she felt she was entitled to, and goes out of her way to make sure she knows this before finally coming to terms with it.
* StockPunishment: The teaser for "Francine's Pilfered Paper" takes place in the Puritan era, and she is punished for plagiarism in this way.
* TokenMinority: Francine's family is Jewish in an apparently mainly Christian community.
* TomboyAndGirlyGirl: Her and Muffy.
* TookALevelInKindness: In earlier seasons she was notorious for her constant teasing of Arthur purely for her own amusement, but as of more recent seasons this bad habit has become far less frequent.
* {{Tsundere}}: Comes off as this occasionally, especially towards Arthur.
* TyrantTakesTheHelm: Main plot point in S1's "Francine Frensky, Superstar". Only after Mr. Ratburn intervened (after what amounted to the entire class sabotaging the play rehearsal) was everything put back into place.
* WeWantOurJerkBack: Happens in S1's "Meek For A Week"', which nearly caused the group's team to lose a hockey match. They got the jerk back when her BerserkButton was pushed.
* WithFriendsLikeThese: Her and most of the cast, but it is more prominent between her with Muffy. Sort of goes both ways with Muffy, considering the latter is so often a RichBitch, and appears totally clueless as to why Francine doesn't have the same amount of money or cool gadgets that she does--among other things Muffy is clueless about.

[[folder: Mary Alice "Muffy" Crosswire]]
-->'''Voiced by:''' Melissa Altro

Best friend of Francine, since her arrival in 2nd grade. Like the Frensky's, she and her family are monkeys.
* AesopAmnesia: Muffy's lessons in selflessness never seem to last more than an episode. Lampshaded in "Muffy's Art Attack", where she tried to take credit for a series of sculptures that were actually handcrafted by Bailey, just as she took all credit for the cookie recipe she and her friends made in "How the Cookie Crumbles"; Francine does not let this go unnoticed.
* AlphaBitch: Muffy is often a stuck-up and a complete showoff who does not care to see things from other people's perspectives. She is even cruel to her friends from time to time.
* ArtEvolution: Originally drawn with buck teeth.
* BigFancyHouse: A sign of her unknowingly vast wealth, to the point where it actually has a ''mini amusement park'' inside of it.
* BitchInSheepsClothing: When she was first introduced in the main cast in S1's "Arthur and the True Francine".
* BreakTheHaughty: Happens to her semi-frequently.
* CatchPhrase:
** "Vomitrocious!"
** "How rude!"
* ChainOfDeals: Utilizes a small one to get her hands on a World Girl doll in "Cents-less".
* TheClan: Part of a family that is shown to be influential in the transportation industry.
* TheFashionista: Mostly in episodes where she has an opportunity to be in other clothes besides her standard dress.
* {{Flanderization}}: Her (claimed) marketing knowledge.
* GirlyGirl: The most traditionally feminine of the main group.
* HandsGoDown: Subverted in "Sue Ellen Adds it Up."
--> '''Mrs. Bryan''': *Exasperated* Are you going to ask if you can paint the school pink, Muffy? \\
'''Muffy''': *Annoyed* I was going to say "salmon!"
* HeterosexualLifePartners: With Francine.
* HypocriticalHumor:
** Muffy regularly accuses people of being snobs despite being the textbook example herself.
** Her catchphrase, "How rude!", usually spoken in a condescending manner or when she herself is doing something most would also consider rude.
* IntergenerationalFriendship:
** In "The Butler Did... What?", Muffy thought she had this kind of relationship with Bailey. But Francine points out she barely know him personally. To be fair to Muffy, the two are pretty close to one another before she got to know him better by the end of the episode.
** Later episodes show her ''trying'' to have a full version of this with Bailey, though her conversations with him still show shades of ego. For example, Bailey helps Muffy reconnect with her old imaginary friend--but first he has to reassure her she actually has imagination.
* ItsAllAboutMe: Very much, but in later seasons, certain events have mellowed her at different times. For example, she's very upset when she realizes her desire for a bouncy house will result in [[spoiler: losing the cherry tree she's had since she was a kid.]] She also now helps out in a thrift store on occasion.
* JerkWithAHeartOfGold: Despite her flaws, Muffy has a knack for being friendly, cares a lot about her friends, and loves to hang out with them.
* LargeHam: She can be ''really'' dramatic when she wants to be.
* LotsOfLuggage: Muffy tends to struggle without her luxuries, and tries to bring them along when she travels.
* LovableAlphaBitch: She learns from her mistakes and she can be a nice girl.
* ManipulativeBitch: She will do anything to get her way, even if this means lying.
* MeaningfulName: Her street address is 1250 Nouveau Lane. Her family is Nouveau Riche, or new money, as explained below.
* NiceToTheWaiter: To her butler/chauffeur, Bailey.
* OnlyKnownByTheirNickname: Nobody, not even her parents, call Muffy "Mary". Although her mom did give her a FullNameUltimatum (Mary Alice Crosswire) in S1's "The Scare Your Pants Off Club".
* PlotAllergy: In "Poor Muffy", Muffy turns out to be allergic to new carpeting in her house. She stays with the Frenskys for about a week while it's removed.
* RichBitch: She is often labeled a snob and spoiled because of her wealth, condescending attitude and frequent selfishness.
* SlobsVersusSnobs: Between her and Francine. She's the Snob, Francine's the Slob.
* SoreLoser: While not quite as bad as Francine, she has many such moments. Taken to new heights in "The Election", where she blames Arthur for her losing a class election that didn't award anyone any real power.
* TomboyAndGirlyGirl: Her and Francine.
* UpperClassTwit:
** In S13's "The Great [=MacGrady=]", it's shown that she literally ''does not know how'' to do dishes. She simply squirts some dish-washing liquid onto the sink full and expects that to do the job.
** When she learns her family history, she's actually shocked and disgusted when she finds out her family is not akin to royalty, but rather she's descended from commoners and most of her family's wealth comes from her dad's used car business.
** She thinks that using a credit card is not the same as spending money.
* WillNotTellALie: In the teaser for "Arthur and the True Francine" Muffy lies to her friends that she has never told a lie. The episode itself shows that [[BlatantLies she lied about a lot of things]] when she first came to Elwood City.
* WithFriendsLikeThese: Her and Francine. A particularly egregious example is in the episode "My Club Rules" where in Muffy basically decides [[LocalHangout the treehouse]] isn't good enough for her and that she'll start her own club. Muffy basically begins a chain of everyone acting like jerks to everyone else to go form their own clubs.
* YouHaveGotToBeKiddingMe: This is how Muffy responds when she learns that she has to go without spending money for a whole weekend.

[[folder: Alan "The Brain" Powers]]
-->'''Voiced by:''' Luke Reid (seasons 1-4), Steven Crowder (seasons 5-6, Arthur's Perfect Christmas), Alex Hood (seasons 7-9) Paul Stuart Brown (seasons 9-11), James Buckholder (Arthur's Missing Pal), Lyle O'donohue(seasons 12 to 15), Siam Yu (seasons 16-18), Max Friedman Cole (season 18-present)

A young bear, and the smartest among Arthur's friends. Not to be confused with [[WesternAnimation/PinkyAndTheBrain that]] ''[[WesternAnimation/PinkyAndTheBrain other]]'' [[WesternAnimation/PinkyAndTheBrain 90's cartoon character named "The Brain".]]
* AcademicAthlete: Brain is academically brilliant and great at chess. However, he's also great at basketball and soccer.
* TheAce: Besides his intelligence, it is shown that he is also good at various sports. He and Francine are often partners for sport-centric episodes. Academics seems to come more naturally to him. Sports, he has claimed that he practices hard for.
* AmbiguouslyBrown: Brain is [[WordOfGod confirmed]] African-American but doesn't particularly look it since he's a bear. In later seasons, his mother is lighter furred than her son and husband, and is also blonde, meaning the Brain is possibly of mixed race. Then again she had brown hair originally, and as of season 16 is back to that, so it could be dyed.
* TheBartender: At his parents' ice cream shop in later seasons.
* TheBGrade: Brain gets a B- on a test in S9's "Breezy Listening Blues" and concludes that the breezy listening music his parents recently started playing in their music shop is having a deleterious effect on his studies.
* BigWhat: His reaction to his early demise in "Best of the Nest".
* BlackAndNerdy: He's an animal like everyone else a bear to be exact but he celebrates Kwanzaa and has relatives in Senegal.
* BlackBestFriend: Brain and Binky seem to be quite close, despite being polar opposites.
* ButNotTooBlack: His family's celebrating of Kwanza was the only indication of his race, until an African cousin comes over to visit.
* ChildProdigy: He is absolutely brilliant. He's written out of "Buster Spaces Out", wherein the other kids need help building and launching a model rocket. Instead, Carl offers to help, and serves as the team's risk assessor.
* {{Cloudcuckoolander}}: Certainly not as much as someone like [[AgentMulder Buster]], but being the most ridiculously smart in the gang he occasionally will overthink and theorize things to ludicrous extremes, which usually just leaves everybody else bewildered.
* CurbStompBattle: Is easily beaten at chess by the more skilled Rattles in S16's "Brain's Chess Mess".
* DependingOnTheWriter: Brain tends to range between TheSmartGuy who offers helpful information when needed, a StopHavingFunGuy who pops everyone's bubble, and a ChildProdigy who knows how to casually make things some scientists don't know how to make.
* DitzyGenius: He's so smart that he overthinks things.
* FriendlyRivalry: With Francine when it comes to sports, ''usually''.
* InnocentlyInsensitive: Occasionally slips into this when displaying his intelligence, but often more so when he insists on being logical about every small thing. A good example is when he did not trust Sue Ellen to hold up her end of a report they were doing together, and cut her off completely for fear she'd ruin his grade; as Francine points out to him, this was one of his worst habits. Another example is while Buster is away traveling he steps in to help Arthur finish their Robin Hood story, removing all of Buster's fantastical elements for what's scientifically accurate.
* InsufferableGenius: Can slip into this at times. It becomes a plot point in "Bugged".
* MeaningfulName: Alan ''"Brain" Powers''. Appropriate, since he's the most intelligent of his group of friends. Also a PunnyName.
* MrExposition
* NerdsLoveToughSchoolwork: The only one in class who doesn't groan when given a big homework assignment.
* NoNameGiven: It's not really considered appropriate for teachers to address students by their nicknames. Even though it was fudged at first, it was awkward. It didn't become a problem until the TV show began, both because the book narration is from Arthur's perspective and because it is in the third person. Circumstances were such that The Brain had to have a given name, and "Alan" is {{Adorkable}} without being difficult to swallow.
* NotSoAboveItAll: Some episodes, especially later in the show's run, demonstrate that for all his intelligence, Alan is no less prone to bouts of anxiety or irrationality than anyone else. This causes his moments of weakness to appear all the more significant.
* OldShame: An InUniverse example; he was held back in Kindergarten due to emotional issues, something he didn't want his friends in the third grade to know about.
* OnlyKnownByTheirNickname: "The Brain" is only referred to as such by his peers.
* OpeningShoutOut and InternalHomage: The latter of the two is an EpisodeTitleCard, shown in S3's "And Now Let's Talk to Some Kids".
* ThePerfectionist: Being hyper-intelligent, he strives for academic perfection. Becomes a major plot point in "Sue Ellen and the Brainasauros" when he and Sue Ellen are teamed up to do a report, and Brain insists on doing all of the work, which frustrates Sue Ellen to no end. Francine reveals that this has been a bad habit of Brain's since they were small, never trusting his friends to do a good job for fear they'd just bring him down. He finally understands how insensitive he was and finally trusts Sue Ellen with her part in the report.
* RoaringRampageOfRevenge: Goes on one in "Love Notes for Muffy" when she bribes the judges at a science fair; for the most part he just ends up looking foolish for it.
* SanitySlippage: Brain is usually the most calm and approachable of all the kids, but when he feels he's been wronged in some way, he'll become darn near psychotic and start giggling crazily, trying to plot revenge.
* SesquipedalianLoquaciousness: He was the one working on {{Antidisestablishmentarianism}} before the spelling bee in S1's "Arthur's Spelling Trouble".
* SoreLoser: Nowhere near as bad as Francine, but he has his moments. In "Love Notes For Muffy" he tries to get revenge on Muffy for bribing the judges in a science fair they had competed in, where it's implied he felt he was a more deserving winner (Ultimately neither of them do); In "Arthur and the Spelling Bee" the Brain misspells the word "Fear" at the Spell-athon and is thus eliminated, to which he bitterly asks what dictionary was being used.
* TheSmartGuy: A ChildProdigy par excellence.
* SpockSpeak: As a, well, brainy type, he tends to employ a rather formal sentence structure as well as a preference for technical terms.
* {{Technobabble}}: Talks like this a lot, which leaves everyone confused.
* TokenMinority: Brain and his family seem to be the only major African-American characters in the show, what with Brain's friendship and Arthur and all.
* WhyDidItHaveToBeSnakes: He was afraid to go to a pool party because of his aquaphobia, though later seasons remove it, implying that The Brain got over his fear.

[[folder: Shelley "Binky" Barnes]]
--> '''Voiced by:''' Bruce Dinsmore

Another one of Arthur's friends, though also a bully, or once was anyway. He and his family are bulldogs. He plays the clarinet and also dances ballet. He hangs with a group called the "Tough Customers," which has changed its focus since its founding.
* AdultFear:
** In S9's "Binky Goes Nuts", his mother gets worried when he's revealed to have a peanut allergy. Even if the concerns that Mrs. Barnes expresses in "Binky Goes Nuts" seem a bit excessive [[note]] The designated cafeteria table, the label reading, cleaning out all of the allergens in the house, declaring a moratorium on the family's weekly consumption of Chinese food (most such restaurants use peanut oil), giving Binky an adreneline auto-injector ''and'' cell phone, and eventually emailing the parents of every other child in Mr. Ratburn's class [[/note]] , they are realistic.
** He goes through this himself when, in S8's "Thanks a lot, Binky", he imagines Rattles messing up a dangerous rollerblading stunt and hurting himself severely, breaking almost every bone in his body. Then his OpinionChangingDream shows him what would happen if Binky didn't tell the principal like he did, being stuck in the hospital in a full-body cast in agony until all of his bones were healed.
* AmbiguouslyGay: His HiddenDepths reveal an interest for stereotypically gay hobbies such as theater, dance (especially ballet), art, music, culture, and the likes.
---> "I like to read books with lots of pretty flowers. [[SuspiciouslySpecificDenial ...Being crushed by a giant pterodactyl!"]]
* ArtEvolution: In the books his ears were originally drawn flatter on his body and he was fatter.
* BerserkButton: ''NEVER'' speak ill of his mother, unless you want ice cream all over your face.
-->'''Buster:''' [[YourMom Your mother eats gym shorts!]]\\
'''Binky:''' '''''[[BigWhat WHAT?!]]'''''\\
''(Everyone is aghast at Buster's words as a very angry Binky proceeds to smash his ice cream sundae onto Buster's head)''
* TheBigGuy: The biggest and toughest of the main group.
* BigNo: Binky busts out an epic one after a nightmare in S9's "Binky Goes Nuts".
* TheBully: Moves away from this as the series progresses. HiddenDepths are eventually revealed, which moves towards the GentleGiant.
* CharacterDevelopment: Over the course of the series, he goes from a tough school bully to a GentleGiant as more of his HiddenDepths are explored.
* CoolBigBro: He's very nurturing and helpful with Mei-Lin, his younger adoptive sister.
* CouldSayItBut: Binky telling Buster how to liberate his confiscated toy car in "Buster the Lounge Lizard".
* EvenBadMenLoveTheirMamas: He may be a school bully, but he dearly loves his mother. That being said, [[BerserkButton Insult her within earshot at your own peril]].
* EarlyInstallmentWeirdness: In "Buster's Back," Binky offers to trade for a peanut butter sandwich. Then he is given a peanut allergy in a later episode.
* EpisodeTitleCard: Binky blows a bubble gum bubble so big that he is CoveredInGunge when [[BubblegumPopping it pops]], and he gets stuck in the title card circle.
* FatBastard: A heavy-set elementary student who is a Tough Customer, and a school bully. The early seasons played the trope straight, but as the show revealed his CharacterDevelopment and HiddenDepths, it became a subverted trope.
* ForWantOfANail: S20's "Buster's Second Chance" reveals that had Buster not befriended Arthur when they were kids, Binky would become Arthur's friend first, influencing Arthur into becoming a [[{{Jerkass}} Tough Customer]].
* FreudianExcuse: He admits in one episode that his becoming a bully was due to insecurities from being held back in school.
* FriendToAllChildren: While Binky is still a child himself, he befriends D.W. in S3's "The Chips are Down" (to the bafflement of Arthur and friends) and her friend Emily in S13's "The Good, the Bad, and the Binky".
* GagNose: Has the largest nose of the ''Arthur'' cast. [[WordOfGod Marc Brown]] stated it was inspired by a classmate who bullied him and had a potato-like nose.
* GentleGiant: A tall, buff kid with a good heart.
* HeelFaceTurn: Goes from being a school bully and Tough Customer, to a GentleGiant who is one of Arthur's close friends. What started it was Sue Ellen standing up to him in S1's "Bully for Binky".
* HiddenDepths: He's highly cultured and is both a talented ballet dancer and clarinet player. He even admits that being held back has made him very insecure, which led to him becoming a bully.
* JerkWithAHeartOfGold: Seems to vary from sensitive soul who acts tough to genuinely stupid depending on the writer.
* LethalChef: We find out Binky is this when he tries to make dessert for Christmas dinner at a soup kitchen. His attempts include pecan pie with shells and banana bread with peels. Perhaps most egregiously, he forgets to add sugar to his brownies.
* NamedAfterSomebodyFamous: [[spoiler:His great-grandfather, Shelley Barnes.]]
* NamesToRunAwayFromReallyFast: Played straight and subverted; as the school bully, his name used to strike fear into the kids at Lakewood Elementary. But then when you remember that "binky" is another word for pacifier, it loses this.
* OddFriendship: With D.W., ever since S3's "The Chips Are Down". Arthur and his friends are left completely baffled by this.
* OnlyKnownByTheirNickname: [[spoiler: S15's "What's in a Name" reveals that Binky is indeed not his real name. It is, in fact, Shelley, named after his great grandfather. Not only do his parents not call him this, even Binky ''himself'', didn't know.]]
* PlotAllergy: Though earlier episodes imply otherwise, Binky is allergic to peanuts.
* RealMenWearPink: Sleeps with a night light and takes ballet classes. Seems the longer the series continues, the less he tries to hide it. Heck, his shirt is even sort of pinkish-orange!
* SarcasmBlind: He has his moments of this, such as in "Best of the Nest" when he asks his Dad if he can have a computer, to which he was told "when it snows in July". He goes out of his way to ask his friends if it's gonna be cold over the summer.
* SuspiciouslySpecificDenial: In S9's "D.W., Dancing Queen", when Rattles and Molly catches Binky teaching D.W. how to dance (for a school project) and confront him about it, he says he's teaching her martial arts. They buy it.
* TrademarkFavoriteFood: He loves Chinese food, especially (peanut-free) egg rolls.
* UnmanlySecret: [[ZigzaggedTrope Zigzagged]] like crazy. When his character first starts developing unmanly interests, he tries to hide them, but then gets found out anyway. Though some people try to make a big deal of it at first, his perceived fierceness and reputation as a bully allows him to quell any teasing or bullying simply by growls, posturing and death glares. In later seasons, he still sometimes tries to hide it, but just as often is open about it. In Season 15's "I Wanna Hold Your Hand," he doesn't care one bit that his friends in the Tough Customers gang know that he's going to be performing in a clarinet solo, but is terribly afraid that one of them might find out that he still sometimes holds his mother's hand. When they do find out anyway, they chew him out... for not having a juicier, more embarrassing secret!
* WeWantOurJerkBack: Happens to Binky occasionally.
* WhyDidItHaveToBeSnakes: A focal point in S2's "Night Fright", as Binky can get really scared in the dark.

[[folder: Sue Ellen Armstrong]]
--> '''Voiced by:''' Patricia Rodriguez (season 1-8), Jessica Kardos (seasons 9-present)

Arriving in the show in 3rd grade, she and her family are cats. Her father is a diplomat, and her family travels to different countries due to his job.
* ActionGirl: Shown to the skilled in martial arts, particularly Tae-Kwon-Do.
* CarnivoreConfusion: Sue Ellen is a cat. Ratburn is a rat. But they seem to get along fine. There's some sort of humor in the cat character being the vegetarian.
* CatsAreMean: Averted, as she is one of the kindest people in Arthur's group of friends.
* TheDeterminator: Usually a force to be reckoned with once she's set her mind to something; In one episode, she's the only one in the class with the nerve to protest the near-closure of the Sugar Bowl. She was also the first kid to stand up to Binky, eventually prompting him to steer away from bullying.
* EveryoneHatesMath: Apparently, Sue Ellen and her parents aren't that good at math; when it comes time to measure things, they manage by using estimation.
* GirlishPigtails: She wears a pair of them on each side of her head, except they're bunched up and curly.
* GranolaGirl: She becomes one in S8's "Sue Ellen Chickens Out". "Sue Ellen Vegges Out" gives her another level of this, when she decides to become a vegetarian after befriending a pig at a farm she visited. [[note]] Not unlike another [[WesternAnimation/TheSimpsons girl her age]] [[/note]]
* NiceGirl: One of Arthur's nicest friends.
* OnlyChildSyndrome: Main plot point in S2's "Sue Ellen's Little Sister". Come to the point where she spends time with D.W. however...
* OnlySaneWoman: Occasionally fills the shoes of this role.
* ShipTease: S2's "Sue Ellen's Lost Diary" hints that Sue Ellen may have a crush on Arthur, following a debacle with her diary. This is a throwback to the book "Arthur's Valentine" where Arthur has a crush on the new student (Sue Ellen).[[note]] It's also worth noting that [[WordOfGod Marc Brown]] has said she was based on his "girlfriend" when he was younger. [[/note]]
* SixthRanger: Not always in the main group, but important whenever she is.
* SophisticatedAsHell: A downplayed example, but being the daughter of a diplomat and having lived all over the world, she is well-read and is pretty much the class expert on exotic cultures.
* TomboyAndGirlyGirl: Plays the tomboy to Fern's girly girl on occasion.

[[folder: Fern Walters]]
-->'''Voiced by:''' Holly G. Frankel

Originally a background character, she and her family are dogs.
* AmateurSleuth: Fern, like Buster, has this as one of her trademarks. In sharp contrast to Buster though, Fern prefers classic novelized detectives like Sherlock Holmes, Literature/HerculePoirot and Literature/MissMarple, sometimes imitating any of them when she's on a case.
* AscendedExtra: Until S1's "I'm a Poet", she was a relative LivingProp. Lampshaded by Francine once Fern is finally driven to speak after a pushed BerserkButton courtesy of Binky.
-->'''Francine''': That's the most she's said all year!
* BerserkButton: Don't insult her hobbies.
* BewareTheNiceOnes: Francine and the Brain find out first hand in S2's "Draw!" and S12's "War of the Worms" respectively.
* {{Cloudcuckoolander}}: Not to Buster's extent, but still pretty out there.
* EpisodeTitleCard: A shot, taken from S10's "Fern and Persimony Glitchet", that shows her writing. The difference between the other, louder title cards is symbolic of her quiet nature.
* JitterCam: The intro to "Fern's SlumberParty". This does not help Fern at all.
* LetsSeeYOUDoBetter: Fern dares her classmates to put up or shut up when they insult her hobby.
* {{Nerd}}: She is a Mystery Novel {{Fangirl}}, being shown in S2's "Fern's Slumber Party" playing with a Franchise/SherlockHolmes action figure. S11's "Phony Fern" even has her (and George) role-playing as Hercule Poirot.
* NightmareFetishist: Along with mysteries, Fern is ''very'' fond of reading and telling scary stories. She's also known to enact scary pranks on people, or imagine terrible things happening to people while she smiles about it.
* ShrinkingViolet: As the show progresses, she becomes more out-going and socializes more, though she still retains a bit of shyness.
* SixthRanger: Not a part of the main group, but still an occasional friend.
* TomboyAndGirlyGirl: Plays the girly girl to Sue Ellen's tomboy on occasion.
* UnaccustomedAsIAmToPublicSpeaking: Her mom makes her throw a slumber party to improve her confidence. When it works, Fern's mom [[BreakingTheFourthWall gloats a little to the audience]].

[[folder: Prunella Deegan]]
--> '''Voiced by:''' Tamar Kozlov (TV series), Wendee Lee (Arthur's Missing Pal), Bianca Rasmussen (Living Books)

One of the few 4th graders in the show, she and her family are either poodles or rats ([[FlipFlopOfGod official sources disagree]]).
* AlphaBitch: During the earlier seasons. She mellows out a bit once ''Henry Skreever'' and Marina Datillo are introduced to the show in S6's "Prunella's Special Edition".
* BigNo:
** She screams it in the opening of S6's "Prunella's Special Edition", when she discovers that her new book is printed in Braille, and she can't read it.
** Prunella screams it in "Prunella Packs It In", when she dreams that she is in college run by the clown.
** She screams in "Prunella in the Haunted Locker", when she dreams she was attacked by her locker.
* EpisodeTitleCard: [[LargeHam I PREDICT THAT YOU WILL SHORTLY SEE...]] (episode title read out loud), taken from S4's "To Beat or Not to Beat".
* HairDecorations: Wears a bow in her hair.
* HeterosexualLifePartners: With Marina. Occasionally, Muffy would fill this role.
* InconsistentColoring: Her hair is canonically red but up until Season 16 it shifted between brown and red.
* {{Nerd}}: Earlier seasons would show that Prunella and her sister Rubella were obsessed with paranormal phenomena. Her ''massive'' love for ''Henry Skreever'' would later become one of her signature character traits.
* PhonyPsychic: Just like her big sister. Oddly, she still believes her sister even though she's using the same tricks.
* SixthRanger: She's a grade higher than most of the rest of the cast, so she only hangs out with them on occasion.
* YetAnotherChristmasCarol: She goes through one in S4's "Prunella Gets it Twice". Lampshaded when the "Ghost of Presents Past" interweaves Tiny Tim into the story.

[[folder: Marina Datillo]]
-->'''Voiced by:''' Helena Evangeliou

Prunella's friend, also a fourth-grader, who presumably goes to school at Mighty Mountain. Prunella met her in "Prunella's Special Edition" and she's been a recurring character ever since.
* AcademicAthlete: Marina is a bookworm who's also great at gymnastics and yoga. In a brief scene, she's shown playing soccer at school.
* InspirationallyDisadvantaged: Averted. Marina is blind, but does not like people to make a big deal of it. She's also received a massive amount of CharacterDevelopment that's unrelated to her disability, which is somewhat unusual for a kids' show.
* {{Nerd}}: She and Prunella share a deep love of ''Henry Skreever'' novels, and both enjoy paranormal phenomena.
* SatelliteCharacter: She is defined entirely by her relationship with Prunella.

[[folder: Lydia Fox]]
-->'''Voiced by:''' Barbara Mamabolo

An eponymous fox and friend of the third/fourth grade cast who was introduced in later seasons.
* AcademicAthlete: We first encounter Lydia as a new friend of Brain; they met because an injury relegated him to a wheelchair during basketball season. Through this, we find out Lydia is a great basketball player, but is also highly intelligent and plays a mean game of chess. Additionally, she's great at twirling batons.
* HandicappedBadass: She may be in a wheelchair, but she's good at basketball.
* InspirationallyDisadvantaged: Averted. She uses a wheelchair, but it's not her only characteristic, and she's quite opposed to being given sympathy based on the wheelchair alone.
* {{Retcon}}: She originated as the winning character of a kids' contest, where her submitted name was Lydia Fox. When the official episode was made, she was never given a last name in dialogue. However, she got the full name Lydia Gordon[[note]]The last name of the kid who won the contest[[/note]] in the episode's credits. When she returned a few years later, the name Lydia Fox was canonized through in-episode dialogue.
* SpeciesSurname: She's a fox with the last name "Fox".
* TomboyAndGirlyGirl: Plays the tomboy to Muffy's girly girl in "Little Miss Meanie" from Season 18.

[[folder: George Lundgren]]
--> '''Voiced by:''' Mitchell Rothpan (season 1-7, APC, AIORnR), Evan Smirnow (season 8), Eleanor Noble (seasons 9-11; seasons 14 - present), Samantha Reynolds (seasons 12-13)

Originally a minor character in the background, he is a moose; a rare sight in the show. He is a young boy who has special talent in wood-carving and building, and is a skilled ventriloquist. He is often accompanied by Wally, his giraffe dummy.
* TheAnnouncer: Takes up this hobby in "Baseball Blues".
* {{Adorkable}}: George is incredibly awkward around other people (in part because of his horns), and spends less time talking to living people than he does to his ventriloquist's dummy, Wally, ''which he made himself''.
* AscendedExtra: Though George existed since the beginning of the show, it was quite a long time before he was made into a full-fledged character, in S3's "Arthur's Dummy Disaster". Since then there have been more George-centric episodes.
* BigNo: Three instances:
** S8's Desk Wars, when his bubble-gum stegosaurus model is destroyed.
** S9's George Blows His Top, when Arthur asks him if George can tell him the time. He replies, "NO!! What is it with you people? GET YOUR OWN WATCH!!"
** S14's "Follow the Bouncing Ball", where his painstakingly arranged dominoes are knocked over by Francine.
* ButtMonkey: He is often the subject of Binky's bullying in the earlier seasons prior to his characterization. Once he becomes more important, he still frequently gets forgotten or ignored by his friends.
* ConsultingMisterPuppet...Who is regularly poached for advice.
* ForgettableCharacter: Initially ''nobody'' could remember him. It's gotten better recently, but still occasionally comes up.
* LIsForDyslexia: Although the original portrayal is closer to AttentionDeficitOohShiny.
* MrImagination: Has many imagination sequences.
* MysteriousProtector: This is George's entire relationship with his classmates, until they get to know him.
* OnlySaneMan: On occasion; a notable example is "Do You Speak George?" when everyone insists on speaking only their own made up languages.
* SixthRanger: The main group frequently forget he even exists, so he only tags along on occasions.
* TruthInTelevision: Students with disabilities can submit exams and assignments in an alternate format, if they have documented their disability in advance.
* {{Ventriloquism}}: With Wally.

[[folder: Carl Gold]]
--> '''Voiced by:''' Dwayne Hill (season 13), Dylan Hoerner (seasons 14-present)

A young male rabbit who befriends George in season thirteen, and is later introduced to George's classmates. Carl has [[UsefulNotes/AspergerSyndrome Asperger's Syndrome]].
* AnythingButThat: The first time that Carl sees Wally, he starts to [[GottaGetYourHeadTogether hold his head and panic]]. By the time of "Carl's Concerto," he's over it, though.
* BlessedWithSuck: In the sense that having rabbit ears only heightens his sensitivity to auditory stimuli.
* ChildProdigy: In "Buster Spaces Out", Carl is able to easily serve as a risk assessor for Buster's model rocket launch, filling in for an indisposed Alan.
* InspirationallyDisadvantaged: [[spoiler: While the writers are usually very good about avoiding this trope, Carl's role in "He Said, He Said" is a Type B example. Carl is able to remember the events of a Bionic Bunny special better than Arthur, Buster, or George can.]]
* LongSpeechTeaTime: George gets Carl going on a monologue about trains. Since George can't get Carl to stop, it turns into the framing device for the story of how they met.
* NotActuallyTheUltimateQuestion: When George shows Carl a picture he drew of a lion, he asks, "What do you think of my lion?" Carl says that lions used to live all over the world, but now live only In Africa and Asia. George has to clarify that he was asking Carl's opinion of the drawing.
* PhotographicMemory: Implied in a couple of episodes.
* RailEnthusiast: Carl has books about trains, loves to put together train puzzles, and keeps a journal of train illustrations.
* SatelliteCharacter: Played with. Carl initially meets George, and meets his other peers later. While he does try to get along with the other kids, George still acts as an intermediary for them sometimes. In a straight example, Carl's mom only ever appears to support Carl himself.
* SpellMyNameWithAnS: Closed captioning spells Carl's surname as "Gold," but Arthur Wiki spells it as "Gould".

[[folder: Jenna Morgan]]
-->'''Voiced by:''' Brigid Tierney

Another former background character in Arthur's class, she is a cat, entirely different from Sue Ellen though.
* TheAce: It is mentioned that Jenna is also good at sports, mostly at the ones Francine is not good at.
* AscendedExtra: Like George, it was quite a while before she became a character with a personality. Despite having only one episode with her as the main focus in the show's 15 seasons (S7's "Jenna's Bedtime Blues"), she is maintained as a prominent secondary character.
* TheChewToy: She becomes this in "The Good Sport" when Francine continually badgers her for winning Athlete of the Year, and is fully aware that everyone thinks Francine should've gotten it. The two eventually make up though.
* DarkHorseVictory: Everybody was floored when she was awarded the Athlete of the Year Award over Francine.
* EmbarrassingDampSheets: In "Jenna's Bedtime Blues", she is revealed to have this problem.
* InformedAbility: In S6's "The Good Sport" we're told that Jenna excels in a number of sports that it's hard to imagine her doing. This seems like a one-off joke at first, but later episodes actually show her playing those sports.
* PlotAllergy: [[{{Irony}} Jenna is a cat who's allergic to milk]].
* MauveShirt: She has gotten a few spotlight episodes, but much less than the rest of the cast, and still generally remains underdeveloped. She is eventually depicted as Maria's confidant in "Maria Speaks."
* OutOfFocus: Jenna has only spoken a few times since season 9.
* WhyDidItHaveToBeSnakes: Jenna's reluctance to put on her pull-ups as shown in her only focus episode, S7's "Jenna's Bedtime Blues".

[[folder: Ladonna Compson]]
--> '''Voiced by:''' Krystal Meadows

The Compsons are a family of rabbits with tan fur. They moved from Louisiana to Elwood City in the Season 16 premiere, "Based on a True Story". Ladonna is the third of four siblings. She has a penchant for oral storytelling, similar to Fern's love of poetry, or Sue Ellen's journaling hobby.
* BigEater: So much so that her father calls her a "garbage disposal with legs". The only thing she won't eat is [[StockYuck beets]].
* BunniesForCuteness: Quite a good-looking rabbit.
* CoolBigSis: She has her moments, particularly during "Adventures in Budylon." [[spoiler: She steps up to teach Bud how to tie shoelaces.]]
* TheFriendNobodyLikes: Downplayed. Ladonna's tendency to tell tall tales makes her the most likely of Arthur's friends to upset everyone else, especially when she first moves into town. [[spoiler:"Ladonna's Like List" explores the concept of Ladonna's likeability.]]
* GenkiGirl: Is quite the chatterbox and can be rather chipper at the right times. Especially when snowy season comes around, as seen in "Waiting for Snow"; Ladonna [[{{Squee}} squeeing]] in excitement becomes a RunningGag in the episode.
* MotorMouth: Initially introduced as such, telling tall tales in the hopes of impressing her would-be friends.
* StockYuck: She can't stand beets; just ''looking'' at beets upsets her stomach.
* TrademarkFavoriteFood: Cake, [[ King cake]] in particular.

[[folder: Maria Pappas]]
-->'''Voiced by:''' Stacey Depass

A background character frequently seen as a member of Mr. Ratburn's class; she is a rabbit.
* ADayInTheLimelight: "Maria Speaks", her first speaking role to date.
* AscendedExtra: One of the most recognizable background characters, it was not until ''Season 19'' that Maria was actually given either a name or an actual speaking part. While far removed from being a main character, she is never far out of view at Lakewood Elementary.
* BunniesForCuteness: Probably a big part of why she stands out despite being in the background.
* FriendToAllLivingThings: So much so that she is able to speak perfectly well when addressing animals.
* HeterosexualLifePartners: In a loose sense, as Jenna seems to be the only person Maria is otherwise able to confide to under normal circumstances.
* OutOfFocus: More so than any other character before her first lead role in Season 19.
* ShrinkingViolet: She desperately tries to hide her stutter from the rest of her classmates.
* SpeechImpediment: We find out that Maria suffers from a chronic stutter; with a little help however, she is slowly overcoming it.
* TheVoiceless: Until Season 19, she was this. So much so that Arthur can't remember ever hearing her speak.

[[folder: The Tough Customers]]
->''"We're not bullies. We're kids who have a hard time expressing our emotions in a constructive manner." - Rattles''

The Tough Customers are a gang of bullies at Lakewood Elementary School, founded by Binky, who is the one member who is not in the fourth grade. In "Arthur's Big Hit", Binky decides to get rid of the club, but in later episodes the club is still there. They hang out on the jungle gym (aka: The Tower of Pain), and also have an entire lunch table reserved for themselves. In early episodes, especially Season One and Two, they were portrayed as malevolent malcontents, but this lessened as time went on. Initially, there were many members, including Binky, Rattles, Molly, but the core three are the only of the original club to remain: none of the others are seen very frequently after Season Four. Later, Molly, Rattles, and Binky are joined by Slink, who was previously just a one-shot character from an earlier episode. From then onward, those four are consistently portrayed as the entirety of the group.
* AerithAndBob: Molly, ''Rattles'', and '''''Slink'''''?
* AffectionateNickname: It's subtle, but Rattles often refers to Molly by "Moll" rather than her actual name. Both of them refer to Binky as "Binks" on several occasions.
* BlueAndOrangeMorality: Due to their extreme displays HypocriticalHumor. In one episode, Arthur proclaims that he's a thief to gain acceptance to their group, and they openly welcome him and congratulate him on his "art." Then when it's revealed he wasn't honest, Binky and Rattles berate him for lying.
* CharacterTics: Frequently and consistently seen with their rollerblades and skateboards.
* CharacterDevelopment: They're introduced as a GangOfBullies of sorts, but they slowly reveal their nicer and more sensitive sides during the series. As of "The Last Tough Customer", they decide to abandon their bullying ways altogether.
* CharacterizationMarchesOn: They become less obvious bullies and just kids who can sometimes be thoughtless and mean. They also channel their energy more constructively, going from malicious bullying to consumer advocacy.
* DependingOnTheWriter: Whether they're actually legitimately malicious or just rougher and tougher than most of the other students.
* DiminishingVillainThreat: In early seasons, they're truly nasty and unkind to other students. By Season Eight, the worst they do is claim the jungle gym for themselves and bar everyone else from playing there, and occasionally throw water balloons at other students. [[spoiler:By S16's "The Last Tough Customer", they decide to abandon their tough act altogether.]]
* EvenBadMenLoveTheirMamas: Binky and Rattles play it straight, with Binky's BerserkButton involving insults about his mother . Molly is a gender-inverted example.
* EveryoneHasStandards: When they realized they might have unintentionally hurt Pal in "Arthur Cleans Up", they look notably dismayed and upset.
* ForWantOfANail: In S20's "Buster's Second Chance", both the Tough Customers' evolution into [[JerkWithAHeartOfGold bullies with softer sides]] and HiddenDepths, and their eventual disbandment as a group in S19 depended on Buster befriending Arthur. If Buster hadn't done so, they would have continued to terrorize Elwood City.
* GangOfBullies: As close as they could get on ''Arthur'', anyway.
* GoKartingWithBowser: Binky hangs out with Arthur and his friends on a regular basis, and Molly and Rattles can be seen doing the same in "Don't Ask Muffy" and "Bugged".
* HiddenDepths: All of the Tough Customers have this, especially Rattles, Molly, and Binky.
* JerkWithAHeartOfGold: As quoted by Rattles above, all of the Tough Customers are deep down, very nice people with personal hobbies they enjoy, and even help out Arthur and his friends on multiple occasions (especially Binky, who hangs out with them as well as D.W. regularly). They just don't know how to express themselves in a more socially acceptable manner other than acting tough. [[spoiler:By S16's "The Last Tough Customer", they avert it by dropping their bullying ways and shape up.]]
* LocalHangout: The jungle gym, which they call the "Tower of Pain". Oddly enough, they can be frequently found at the library, as seen in "Sue Ellen's Lost Diary" and "Arthur Makes Waves". They also make the Sugar Bowl their hangout in S20's "Buster's Second Chance" in an alternate timeline where Buster didn't befriend Arthur.
* MeaningfulName: On one hand, Rattles and Binky are named after children/infant toys and objects, suggesting they really aren't as tough as they appear. On the other hand, we have Molly, whose name means "bitter", and Slink, a term to describe a quiet, stealthy walk.
* MetalHead: Molly, Rattles, Slink, and maybe Binky.
* NoNameGiven: A few of the Tough Customer "extras" have names, like the male cat named Kieper, the female cat named Fletcher, and the male bear named Billy, but others remain unnamed such as a male dog, a male rabbit, and a female aardvark.
* NotEvilJustMisunderstood: What Rattles claims he and his friends are in S14's "D.W., Queen of the Comeback", as quoted above.
* PetTheDog: In S8's "D.W., Dancing Queen", both Molly and Rattles step up to help D.W. with her ballet performance when Binky twists his ankle and is unable to dance onstage with her.
* RealMenWearPink: Especially Binky and later Rattles, but all of them dance ballet at some point. Binky, Slink, Molly, and Rattles all take part in a barbershop routine for the Summer Serenade in "D.W. Beats All".
* SoapboxSadie: Downplayed. They go from bullying their schoolmates to picketing businesses to protest problems like extortion and unhealthy fast food. They usually don't overshoot it, though.
* SchoolBullyingIsHarmless: [[PlayingWithATrope Sometimes.]]
* {{Tomboy}}: All of the girls.
* TrueCompanions: In spite of their faults, they stick by one another and help each other out, as seen in Seasons Eight and Nine. For example, in S8's "Binky Goes Nuts", when it was discovered that Binky was allergic to peanuts, Molly acted as bodyguard and prevented students with said food from sitting near him in order to preserve his health. They also helped Rattles get along with his new twin step-siblings, even giving him a slang dictionary so he can understand his step-sister's lingo better.
* VillainsOutShopping: Rather hilariously, Molly and Rattles can be seen at the front of the crowd at the meeting for concerned citizens in "The Scare-Your-Pants-Off Club".
* YoungerThanTheyLook: They can all pass for high schoolers due to their punk/grunge-like outfits, even though they're about as young as Arthur and his friends.

[[folder: Molly [=MacDonald=]]]
--> '''Voiced by:''' Maggie Castle

A fourth grade rabbit and one of the Tough Customers. She has a younger brother named James, who is friends with D.W.
* ActionGirl: The only female Tough Customer to remain and the only main female skateboarder.
* AloofBigSister: Averted. One might think she would be this, but she is close with James.
* AlliterativeName: Molly [=MacDonald=]
* AscendedExtra: She started off as a generic bully girl in the Tough Customers, but later episodes gave her a MoralityPet in the form of her younger brother, a hidden creative side, a more relaxed personality (in comparison), and an overall more sympathetic presentation.
* TheAtoner: Becomes this in S19's "The Last Tough Customer" [[spoiler:when she realizes that James is adopting her bullying ways, and decides to try turning a new leaf.]]
* BerserkButton: If anyone tries to take the "Tower of Pain" from her, as seen in "The Law of the Jungle Gym".
* BlindingBangs: Her eyes have only been seen very briefly in a few episodes, such as "Agent of Change" and "Arthur, World's Greatest Gleeper".
* CoolBoard: Her skateboard is black and wrapped with barbed wire around the middle.
* CoolBigSis: When James needs help, he goes to Molly.
* ADayInTheLimelight: [[spoiler: Season twenty one's "Take A Hike, Molly!"]]
* DefrostingIceQueen: Over the course of the series, though not especially evident. Most apparent in "Arthur Makes Waves".
* DrillSergeantNasty: When coaching her younger brother for his swim meet.
* EvenEvilHasLovedOnes: She's very close to her little brother James, despite her tough act. [[spoiler:When James TookALevelInJerkass just by watching her, Molly has a HeelRealization and resolves to reform herself for his sake.]]
* ExpositoryHairstyleChange: [[spoiler:During her StartOfDarkness, she changes her bun to her current tomboyish bob after she is bullied.]]
* FieryRedhead: Her hair's more a reddish-brown, but she acts like this on occasion, often when she gets lines.
* ForbiddenFriendship: With Arthur, prominently in one episode, though they keep it a secret due to their respective friends' disapproval. [[AesopAmnesia Though the writers seem to have forgotten about it,]] [[{{Shipping}} the shippers have not.]]
* ForWantOfANail: S20's "Buster's Second Chance reveals that [[spoiler:she would still remain a bully and Tough Customer had Buster not befriended Arthur at the fated sandbox.]]
* FreudianExcuse: [[spoiler:She was bullied a lot when she was younger, her classmates tormenting her by calling her "[[MaliciousMisnaming Muffin Head]]" and destroying her sandcastles. The experience hardened her heart and made her act tough, and in time she became a bully herself.]]
* HeelRealization: "The Last Tough Customer" is this for her after seeing James picking up her bully habits.
* HiddenDepths: She cares a great amount for her brother and Mom, is interested by storytelling and animation techniques, and is concerned by the lack of independent female characters in media.
* ImpliedDeathThreat: We don't hear what she said to Muffy in "The Law of the Jungle Gym", but even the other Tough Customers thought she went too far.
* ImportantHaircut: [[spoiler:Her hair used to be longer and put up in a bun right on top of her head when she was in preschool. But after she was bullied, she let her hair loose and transformed into her current bob in an attempt to adopt a tougher image.]]
* JerkWithAHeartOfGold: Once took great pride in her bullying ways, but deep down is a well-meaning and somewhat insecure girl.
* JustFriends: With all of the male Tough Customers, as well as Arthur.
* KickTheDog: In S16's "The Last Tough Customer", she cruelly pokes fun at George's [[spoiler:dyslexia]], causing the boy to run off and cry. [[EveryoneHasStandards Even Binky, who regularly picks on George thought that wasn't okay]].
* LeanAndMean: Perhaps it's just because she's older and taller, but she's noticeably thinner than the main cast. This is especially apparent when she's standing next to the male Tough Customers, who are more stocky and muscular than her.
* MaliciousMisnaming: [[spoiler:"Muffin Head", due to how her bun was put right on top of her head when she was a preschooler.]]
* MeaningfulName: Her first name means "bitter", which certainly suits her malicious personality in the early seasons. The derivation of her surname is from the Gaelic "Mac Dhomhnuill", translating as "The son of Donald". It is said that the personal name "Donald" translates as "world-rule". Molly is a bully who rules the playground.
* MasculineGirlFeminineBoy: Compare her distinct lack of traditionally female interests and her rough-and-tough appearance to [[RealMenWearPink Binky's activities.]]
* NotSoAboveItAll: In "Arthur Makes Waves", she discovers she has a lot in common with Arthur after she stops trying to act cooler than him all the time.
* OddNameOut: She has a normal name compared to Rattles, Binky, and Slink.
* OffModel: At some points in early episodes, her BlindingBangs are shorter than usual, but her eyes don't show at all, giving the impression she has no eyes.
* OneOfTheBoys: To the extent of some ViewerGenderConfusion, as her demeanor and activities barely portray a hint of femininity.
** At one point, the male Tough Customers imagined her in a dress and were weirded out by the very idea.
** She took part in a barbershop quartet with Binky, Slink, and Rattles. All four wore traditional male barbershop costumes.
** In an ImagineSpot of 50's society, Arthur and his friends are shown wearing gendered clothing, letterman sweaters for the boys, poodle skirts for the girls, while the Tough Customers are depicted as greasers. Molly is wearing a dark leather jacket and jeans right alongside her male friends.
* PetTheDog:
** In "Law of the Jungle Gym", she can be seen several times being kind to a stray cat.
** She is often very kind to her younger brother, and much more patient with him than Arthur is with D.W.
** When other students come to her for advice, she tells them her best ideas and takes time to talk with them even though she would rather be skateboarding.
** "The Last Tough Customer" is one giant moment for her [[spoiler:combined with TheAtoner, HeelRealization, and HeelFaceTurn.]]
* PintSizedPowerhouse: A subtler example than most, but when she is arm-wrestling with Binky, she gives as good as she gets even though he's taller, heavier, and stronger than her.
* PlatonicLifePartners: As of Seasons Eight and Nine, Molly and Rattles are almost never seen apart, even for mundane activities such as walking the dog, or special occasions such as dancing ballet together.
* PositiveDiscrimination: She is depicted as the most intelligent, capable, and, besides Binky, sympathetic Tough Customer, and though she still remains tough, her bullying of other kids is less and less prominent in later seasons.
* SleevesAreForWimps: A rare female example. Molly is almost always seen wearing a denim jacket as a shirt with ragged edges from ripping off the sleeves.
* SiblingYinYang: Tough, confrontational Molly and her quiet, unassuming younger brother James.
* SpellMyNameWithAnS: It's '''[=MacDonald=]''', not [="McDonald"=].
* StartOfDarkness: [[spoiler:Turns out she was a victim of bullying herself. Seeing James start to repeat the pattern prompts her HeelRealization.]]
* TheStoic: As a result of her BlindingBangs that hide her eyes, it's difficult to gauge her emotion when she isn't speaking.
* TertiarySexualCharacteristics: Mostly absent. The only physical indication of her gender is her bob, but that helps little when she's standing beside fellow Tough Customer Slink, who is male and has hair that's longer than hers.
* ThoseTwoBadGuys: While she often initially appeared in the background of some scenes along with other Tough Customers, Season Five onwards seems to be going forward with this route for her and Rattles.
* {{Tomboy}}: Out of all the girls on the show, Molly is probably the quintessential example. Binky had to convince her to dance ballet by telling her [[BlatantLies it was a new martial arts style]]. Undoubtedly the most aggressive female character on the show, even after her CharacterDevelopment.
* UsedToBeASweetKid: [[spoiler:She was a sweet little girl until she became a bullying victim in preschool. After that, she [[TookALevelInJerkass became a Tough Customer]].]]
* WomenAreWiser: From Season Eight onwards, most episodes featuring the Tough Customers portray her as the most level-headed and realistically-minded of the group.

[[folder: Rattles Ciccone]]
--> '''Voiced by:''' Scott Beaudin (season 14-present)

A fourth grader who seems to alternate between being a cat, a dog, and a bear.[[note]]Since the nose is basically the same for all three, the ear shape is how to tell the difference. Rattles only took off his hat 4 times in 18 seasons, leaving plenty of time for the animators to forget minor details.[[/note]] Another one of the Tough Customers.
* BewareOfViciousDog: He owns a mean, snarling dog, aptly named "Crusher." Said dog [[TookALevelInKindness later becomes nicer]] due to the influence of Grandma Thora's dog Killer, and Francine's cat Nemo.
* BookDumb: He has an extensive vocabulary, but has trouble spelling, as seen in "The Play's The Thing".
* CallingMeALogarithm: Inverted. He uses words he doesn't know to insult people, such as "bibliophile" and "philanthropist".
* CatsAreMean: As stated above, he alternates between being a cat, dog and/or bear, though he's still not very nice either way.
* CoolPeopleRebelAgainstAuthority: Played straight with him most of the time, but he is occasionally shown to have a certain degree of respect for those in charge.
-->Rattles: [[ItMakesSenseInContext (Protesting the idea that Mr. Ratburn would wear socks with holes in them)]] '''Mr. Ratburn wouldn't wear no sock full of holes! He's a very upstanding kind of guy.'''

-->Rattles: (Upset when someone puts trash in the recycling bin) Yo! It's paper only! Can't you read?!
* CurbStompBattle: He won his chess match against Brain in S16's "Brain's Chess Mess" pretty quickly.
* DarkIsEvil: A bully and one of the only two kids to have a recurring black article of clothing (in his case, a black jacket he constantly wears). However, it's also subverted in later seasons, where he reveals himself to be a decent guy underneath his tough image, with hobbies of his own.
* ADayInTheLimelight: S19's "Whip, Mix, Blend.", where he deals with his mother's divorce and remarriage, and learning how to live with his twin step-siblings.
* HellBentForLeather: His dark jacket resembles one of these.
* HiddenDepths: He's a very skilled chess player, enough to teach Brain's Chess Club how to play better, and likes [[RealMenWearPink knitting and sewing]]. His vocabulary also includes words that are above his school grade. In S16's "Brain's Chess Mess", he declines Brain's offer to do his homework in return for joining the Chess Club, on the reason it'll "deprive [Rattles] of his education."
* HypocriticalHumor: Yells at a guy for tossing regular trash into a paper-only recycling bin, minutes before intimidating some random children into giving their ice cream to him and Molly.
* {{Jerkass}}: Probably the most consistently antagonistic of the Tough Customers. He becomes nicer in later seasons, though.
* JerkWithAHeartOfGold: Despite his tough, bullying ways, he's still an okay guy deep down.
* {{Joisey}}: His voice in later seasons has shades of this.
* NamesToRunAwayFromReallyFast: If his name refers to "Rattles" as in "Rattlesnake," he fits this. If it's the ''other'' kind of rattle, then not at all.
* NiceHat: He is almost never seen without his red baseball cap, always worn backwards.
* NotEvilJustMisunderstood: He doesn't see himself as a bully, and took offense at being called one by D.W. in S14's "D.W., Queen of the Comeback".
* NotSoDifferent:
** With Arthur towards the end S14's "Arthur Unravels" - turns out he likes knitting, too, but kept it a secret from the other Tough Customers. His response to Binky, Molly, and Slink looking at him in surprise after Dr. Fugue outs him as a member of his knitting club, is to shrug and smile sheepishly as if to say, "Guilty as charged."
** Seasons 14 and 16 reveal that he also has a food allergy just like Binky, except in his case he's lactose intolerant.
* OffModel: He had a dark brown tuft of hair in early seasons, but after Season 8, it was changed to light gray to match his skin.
* PetTheDog:
** As mentioned in the Tough Customers' folder, he and Molly help D.W. with her school ballet project after Binky twists his ankle.
** He also tries to help D.W. come up with good comebacks against the [[BrattyHalfPint Tibble twins]] in S14's "D.W., Queen of the Comeback", even though he personally thinks the kids' vendetta is ridiculous and initially suggests to D.W. that she ignore the Tibbles.
* PlatonicLifePartners: As of Seasons 8 and 9, Molly and Rattles are almost never seen apart, even for mundane activities such as walking the dog, or special occasions, such as dancing ballet together.
* PlayingSick: [[spoiler:He fakes a stomachache on the day of a chess tournament in S16's "Brain's Chess Mess", as part of a gambit to get Brain to play against a particularly hard opponent without his help, because he had faith Brain can do it. It works.]]
* PlotAllergy: Seasons 14 and 16 reveal that he's lactose intolerant.
* RealMenWearPink: His interests include sewing and knitting.
* RecurringExtra: He can often be seen in background scenes, more so than any of the other Tough Customers.
* SophisticatedAsHell: He often makes quite eloquent and mature remarks, but they end up sounding a bit ridiculous due to his exaggerated {{Joisey}} accent that makes his voice seem a bit thuggish, and his lack of knowledge in regards to what the words actually mean.
* StockForeignName: His surname is "Ciccone", suggesting he is of Italian descent.
* ThatLiarLies: In S1's "Arthur, World's Greatest Gleeper". After he learns that Arthur lied about being able to gleep, he responds with a tirade that ends with "lying lie face".
* ThoseTwoBadGuys: While he often initially appeared in the background of some scenes along with other Tough Customers, Season 5 onwards seems to be going forward with this route for him and Molly.
* TookALevelInKindness: Like Binky before him, he started off as a school bully in early seasons, then got hit with CharacterDevelopment and HiddenDepths the longer the show ran. Prominent examples include helping D.W. with her ballet performance ("D.W., Dancing Queen") and coming up with good insults for her to use against the Tibble twins ("D.W., Queen of the Comeback"), befriending and teaching Brain and his friends how to play chess ("Brain's Chess Mess"), and putting up with Carl's autism without complaint ("Carl's Concerto").
* UngratefulBastard: In S8's "Thanks a Lot, Binky", Rattles gets mad at Binky for "squealing" on him for trying to pull off a dangerous rollerblading stunt with his friends, even though said stunt would've broken every bone in his body and put him in the hospital for a very long time.
* WhatTheHellHero: He harshly calls out Arthur for lying to him and his friends in S1's "Arthur, World's Greatest Gleeper", making it a point to sit on Arthur and bounce a ball on Arthur's head as he did so.
* WhoNamesTheirKidDude: Seriously, ''Rattles''?

[[folder: Slink]]
--> '''Voiced by:''' Michael Yarmush

A fourth grade rabbit with a tanner complexion than Molly, and another Tough Customer.
* AscendedExtra: Initially a single-episode bully character from "Buster and the Daredevils", but is a recurring member of the Tough Customers by Season Six.
* BlindingBangs: Due to his hair. His bangs are even longer than Molly's, cover roughly half his face, and his eyes have only been seen once.
* ADayInTheLimelight: [[spoiler: Season twenty one's "Slink's Special Talent."]]
* DarkIsEvil: A bully and one of the only two kids to have a recurring black article of clothing (in his case, a black shirt with a red lightning bolt on the front).
* HeterosexualLifePartners: With Toby, at least until their efforts to humiliate Buster failed, and now they don't even attend the same school.
* MeaningfulName: His moniker suggests that he may not be of the best repute. He isn't.
* RingRingCrunch: [[spoiler: "Slink's Special Talent" sees the lackadaisical Slink respond to his alarm clock by hitting the snooze button, putting in a drawer, and finally throwing it offscreen.]]
* SeriesContinuityError: When Slink was first introduced, he attended Mighty Mountain. He later appears at Lakewood Elementary with no explanation offered.
* WhoNamesTheirKidDude: His name really takes the cake for this.
* WildHair: The only elementary school boy to have longer hair.

!Younger cast
[[folder:Dora Winifred "D.W." Read]]
-->'''Voiced by:''' Helena McAnham (Living Books, Arthur's Teacher Trouble game, Arthur's Birthday game), Michael Caloz (first three seasons), Oliver Graigner (seasons four to six, Arthur's Perfect Christmas), Jason Szwimmer (seasons 7-10, It's Only Rock And Roll), Robert Naylor (seasons 11-15), Jake Beale (seasons 16-17), Andrew Dayton (seasons 18 to 19), Christian Destefano (seasons 20-present)

Younger sister of Arthur and middle child of the Reads, and often the main character of episodes focusing on the younger cast.
* AesopAmnesia:
** She always comes back to create trouble for Arthur no matter how many times she sees the error of her ways.
** In "More!" D.W. finally realizes how foolish she'd been to be chasing her friends and family for money....Only to be caught again asking Grandma Thora at the end of the episode.
* AllGirlsLikePonies: D.W. adores them. Her favorite idea for a holiday is Pony Day. Oh, and she loves unicorns too.
* AnnoyingYoungerSibling: To annoyingly frustrating degrees.
* BerserkButton:
** Teasing her about her full name, anything involving her snowball, or saying that Unicorns and other fantasy creatures are not real.
** In "DW The Picky Eater", being served spinach was a huge pet peeve of hers.
* BigSisterBully: Towards Kate at times; most notably when she threatens to pinch her for touching her toys, though unlike other times, she gets grounded for once. [[InvertedTrope Inverted]] with Arthur at her worst.
* BlatantLies: She's certainly not the most honest child. In "Go To Your Room, D.W.", when she gets sent to her room for being mean to Kate, she tells Nadine a bunch of falsified memories of how her parents abused her, like when they forced her to be Arthur's slave when he was sick and not allowing her to attend Aunt Lucy's wedding. Nadine doesn't buy a word of it.
* BoyishShortHair: Has a bob-cut. Her TraumaticHaircut in "DW Queen Of The Comeback" is even shorter.
* BrattyHalfPint: Whines when things don't go her way.
* CallBack: Upon hearing of Kate's birth in "Arthur's Baby," D.W. does a cartwheel, a skill she worked hard to master in "D.W. Flips."
* ChekhovsGunman: After an entire episode of [[UnwantedAssistance getting in the way]], D.W. saves her aunt Lucy's wedding in "D.W. Thinks Big".
* CompanionCube: Her snowball.
* ChromaticArrangement: In one episode, The Tibble twins do this to her clothes.
* DeadpanSnarker: Has unfailing snark.
* DoesNotLikeSpam: [[PunctuatedForEmphasis "I! HATE! SPINACH!!!"]] Cue FullNameUltimatum. She got over it, though.
* EmbarrassingFirstName: Dora.
* EmbarrassingMiddleName: Winifred.
* FullNameUltimatum: Heard often due to the amount of trouble she gets in.
* FoolishSiblingResponsibleSibling: The Foolish to Arthur's Responsible.
* GirlsLoveStuffedAnimals: She has a large collection of stuffed animals and sometimes carries them around, though this seems to show up more often in the books. In the episode ''Never, Never, Never'' she is upset at the thought of getting rid of some.
* GoToYourRoom: A frequent punishment of hers. Usually the worst she gets.
* GreenEyedMonster:
** D.W. was originally jealous of Kate, but saw how important her guidance as a big sister would be.
** [[spoiler: Season 20's "That's My Grandma!" sees D.W. getting jealous when Thora becomes the most popular babysitter in Elwood City]].
** A fair amount of episodes center on D.W. wanting something Emily has or has experienced, apparently not too fond of the idea of Emily upstaging her.
* HereWeGoAgain: The final scene in "D.W. Flips" has her begging for horseback riding lessons, after she narrowly avoided both quitting and breaking her neck in gymnastics. She caught Arthur's Chicken Pox.
* IMeantToDoThat: D.W. tries to do a cartwheel, and lands on her back partway through.
--> '''D.W.:''' I was doing a half - sault.
* IdioticPartnerConfession: Usually something like, "Wow, Arthur. This person isn't as scary as you say." In "Arthur's Pet Business," she tells Mrs. Wood that Arthur lost Perky.
* InfantSiblingJealousy: While initially excited at the arrival of Kate, D.W. quickly became annoyed at having a baby around. She went as far as to try and sell her. It takes a lecture from her grandmother for D.W. to come around to embracing her little sister.
* InstantExpert: Usually at things that Arthur failed at.
* {{Jerkass}}: Big time. She is known among the other characters for her rudeness and NeverMyFault tendencies.
* JerkWithAHeartOfGold: She's rude, bossy and is a right pain in the backside to Arthur, but deep down she is a good kid, and a couple of times it is shown that she actually loves and cares about her brother.
* KarmaHoudini: She's gotten away with her mischief many times.
* KarmaHoudiniWarranty: There are some occasions in which she ''does'' get punished by her parents.
* LittleMissSnarker: Usually towards Arthur.
* MouthyKid: D.W. can be rude, but sometimes she does have a point.
* NeverMyFault: Usually passes off the blame to Arthur or her friends when she does something wrong and is [[KarmaHoudini rarely punished]] for her actions.
* OnlyKnownByInitials: Nobody calls D.W. "Dora" or "Dora Winifred" unless it's her parents issuing a FullNameUltimatum or they want to deal with a major tantrum. In S2's "D.W. Goes to Washington," Mr. Read actually didn't seem to remember her full name.
-->'''Mr. Read''': Her name is D.W.
-->'''Secret Service member''': That's it? Initials? You didn't give the kid a full name?
* OnlyKnownByTheirNickname: Never called by her full name unless she's in trouble.
* PetTheDog: As seen in [[Heartwarming/{{Arthur}} heartwarming moments]], there are at least a few occasions where does nice things for people.
* PickyEater: Covered in the episode ''D.W. The Picky Eater''. D.W. has a long list of foods which she does not like, most of which are StockYuck vegetables. However, she did learn to like spinach after [[spoiler: being served a restaurant dish in which it was the secret ingredient.]] The teaser for "Kung Fool" also shows that she unexpectedly loved a very green, very foreign dish her dad made, so we can safely assume she's ditched at least some pickiness.
* PinkMeansFeminine: Wears a pink dress.
* RealTime: In "D.W. Gets Lost," Ed Crosswire asks for five minutes of Jane Read's time. This is how long she and D.W. are separated.
* SecurityBlanket: She has one called "blankie" which was the focus of both the book and television story "D.W.'s Lost Blankie." One of the show's title cards depicts her wearing it as a superhero cape.
* SmallNameBigEgo: She's quite the little braggart when she wants to be, usually at Arthur's expense. In "Play It Again, D.W." Arthur recalls the one time D.W. beat Arthur at checkers, and then proceeded to rub his face into it for apparently ''months'' afterward.
* TheStoolPigeon: "MOOOOOOM! Arthur broke a window!"
* TagalongKid: Whenever she hangs out with Arthur's group.
* TomboyAndGirlyGirl:
** Tomboy to Emily's Girly Girl. Emily tends to have more refined manners and much less of a tendency to be bossy or take a leadership role. D.W. also seems like the hardier of the two girls when it comes to roughhousing/generally dealing with the Tibble twins.
** In "Best Enemies," she is the Girly Girl to W.D.'s Tomboy. She loves unicorns while W.D. likes race cars.
* TomboyWithAGirlyStreak: She will climb trees, play catch with Arthur and Dad, and do other tomboyish (for her age) things. That being said, she is also very into unicorns, ponies, and anything pink.
* TookALevelInJerkass: DW becomes this in "DW's Very Bad Mood".
* TraumaticHaircut: In "DW Queen Of The Comeback", her hairstylist cuts off a good chunk of her hair by accident, and DW gets teased by the Tibble twins for it.
* UngratefulBitch: Has shown herself to be this several times.
** PlayedForLaughs in "D.W.'s Perfect Wish," after Arthur has spent an entire afternoon convincing D.W. that she has had a very good year and that she's got many more happy times coming, D.W. actually wishes for Arthur to end up with cake in his face, which is exactly what happens at the dinner table a short time later.
** In another episode, D.W.'s parents spend the afternoon assembling a playset she has been wanting, but has [[KidsPreferBoxes so much more fun playing with the box that when it's ready for her, she doesn't want to try it out]]. Her parents call her out on her lack of consideration, and when she still shows no enthusiasm, they walk off totally deflated.
** In the episode "More!", D.W. is given her first allowance, and she spends the rest of the episode demanding more money when she fears the other kids in her class are getting more. She even gets sent to her room for it at least once when she's called out for being disrespectful.
* UnwittingInstigatorOfDoom: In "My Club Rules," when Arthur and his friends are in the treehouse discussing ideas for their parade float, DW barges in, wanting to hang out with them. Arthur, desperate to get rid of her, lies and says it's a "meeting" of the "Parade Float Club." DW immediately says she wants to "join." They have DW undergo "initiation rituals," such as kicking a bowling ball (which she refuses to do) and drawing a funny picture of Mr. Ratburn. They're so distracted from talking about the float that they're actually focused on making it a real club. A little while later, Muffy makes some snobby comments about how improvements can be made to Arthur's treehouse so it looks like a real clubhouse, and how club dues should be paid in order to implement the improvements. This leads to a fight amongst Arthur and his friends, causing them to form their own separate "clubs." They make up a few days later, of course, but still. It could be argued that if D.W. wouldn't have barged in to begin with, the argument wouldn't have happened and they'd still be discussing float ideas.
* WiseBeyondTheirYears: You'd be hard-pressed to find a four-year-old girl as eloquent and crafty as D.W. in real life.
* WhyDidItHaveToBeSnakes: Saw an octopus up close during a field trip to an aquarium. While recounting the trip to her family, however, [[BlatantLies she claimed to have punched it]].

[[folder: Kate Read]]
-->'''Voiced by:''' Tracy Braunstein

Arthur's and [=DW=]'s younger sister and the youngest Read child.
* BabyTalk: Kate has appeared in episodes where she can speak with other babies and [[AnimalTalk non-anthro animals]].
* GrowingUpSucks: Recently she's been losing her ability to speak with pets, now that she's learning to talk and walk.
* LivingProp: In the episodes that don't focus on her and Pal, although it's justified due to her being a baby.
* SpeaksFluentAnimal: Kate can speak to dogs and cats. However, as of "Paradise Lost", it's revealed she will eventually lose this ability.

[[folder: Timmy and Tommy Tibble]]
-->'''Timmy voiced by:'' Ricky Mabe (seasons 1-5, "Arthur's Perfect Christmas"), Samuel Holden (seasons 6-9, "Arthur - It's Only Rock 'n' Roll"), Tyler Brody-Stein (seasons 10-11), Chris Lortie (seasons 12-13), Dakota Goyo (seasons 14-15), Jacob Ewaniuk (seasons 16-19), Samuel Faraci (seasons 20-present), Max Henry Wolf ("Arthur's Missing Pal")
-->'''Tommy voiced by:''' Jonathan Koensgen (seasons 1-6, "Arthur's Perfect Christmas"), Aaron Grunfeld (seasons 7-8, "Arthur - It's Only Rock 'n' Roll"), Tyler Brody-Stein (season 9), Ryan Tilson (seasons 10-11) Jake Roseman (seasons 12-13), Jake Sim (seasons 14-19), Devan Cohen (seasons 20-present), Madison Danielle ("Arthur's Missing Pal")

A pair of twin bear cub boys, they're often the other major characters in episode focusing on the younger cast.
* AccidentalArt: The Teaser for "A Portrait of the Artist as a Young Tibble".
* {{Alliterative Name}}s: Timmy and Tommy Tibble.
* AnythingYouCanDoICanDoBetter: Sometimes with each other, but usually with D.W. Their web page spells it out.
* BearsAreBadNews: Downplayed. They are bears, but they aren't evil, just really annoying and make D.W. look like a saint in comparison.
* BondOneLiner: D.W. calls to check on things in "Arthur Babysits", while the Tibbles are playing cowboy.
--> '''Timmy''': Arthur can't come to the phone right now. He's all tied up.
* BrattyHalfPint: Both of them, to the point where they make D.W. seem like a complete angel.
* ColorCodedCharacters: Tommy wearing a red scarf, Timmy wearing a blue scarf.
* DoWrongRight: "Mind Your Manners" has a rare take on this trope where the offending party corrects themselves. Molly says that having good manners is about being observant and following the lead of those around you. When Tommy and Timmy see a book in the library they both like, they remember what Molly said, stop themselves, notice The Brain quietly reaching for another book, and quietly resume fighting over the book they're after.
* TheDreaded: ''Nobody'' in town wants to be stuck with the task of babysitting them, and they have quite a bad reputation with anybody else who has witnessed their behavior firsthand.
* EpisodeTitleCard: The boys use fake squid tentacles to scare D.W. off.
* EveryoneHasStandards: They were ''horrified'' upon hearing that D.W. got sent to the hospital because of them throwing a swing at her.
* HairColorDissonance: According to official art (and the books) their fur is brown but within the cartoons they're a greyish color, sometimes with a tint of green.
* HighTurnoverRate: Their babysitters, before Arthur.
* IdenticalTwinIDTag: Tommy wears a blue scarf. His brother Timmy wears a red scarf. That's the only way anyone can tell them apart.
* IKnowYourTrueName: An "Iron Fist" approach will not work when babysitting the Tibbles. Tell them a story, however, and they're more likely to cooperate.
* JerkWithAHeartOfGold: They still have their nice moments despite how bratty they are.
* LionsAndTigersAndHumansOhMy: In the original books, the Tibble Twins and their Grandma were drawn as humans. They have since been anthropomorphized for the television series and latter books.
* RaisedByGrandparents: Raised by their grandma.
* SiblingSenioritySquabble: In "Whistling in the Wind", Tommy is said to be two minutes older, and it's confirmed in "Two Minutes". However, to stop their fussing over it, their grandmother backpedals, saying that they were born at the same time.
* SiblingTeam
* SpoiledBrat: Both of them were spoiled by their grandma, who continues to see them as her little angels, even though that kind of upbringing probably worserned their behavior.
* ThoseTwoGuys: They are twins, so it's rare to see them not by each other's side.
* TokenHuman: Were originally humans in the books, but [[RaceLift got turned into bears in the animated series]].
* TricksterTwins: Cause plenty of mischief, and are twins.
* TwinBanter: It sometimes gets physical.
* UnnecessaryRoughness: They spend an episode basically imitating the Franchise/PowerRangers, and D.W. ends up needing stitches. The boys do apologize, though.
** Otherwise a running gag with them, as they'll often tussle with each other over petty arguments.
* WholePlotReference: [[Theatre/MyFairLady "My Fair Tommy."]]

[[folder: Emily]]
-->'''Voiced by:''' Vanessa Lengies (seasons 1-7), Sally Taylor-Isherwood (seasons 8-present)

D.W.'s best friend and major character in D.W.-centric episodes. She is unique among the show's characters as she is part rabbit, and part ape.
* ADayInTheLimelight: "Emily Swallows a Horse".
* AdaptationDyeJob: Prior to season 6 she had shorter hair. In the books she had her current length but it was the same color as her fur.
* BrattyHalfPint: Almost all of her appearances in S1's "D.W. Flips", where she continues to rubs into D.W.'s face how much of a novice D.W. is compared to her in gymnastics class. [[TookALevelInKindness Later seasons avert this by depicting her as D.W.'s best friend]].
* BunniesForCuteness: Part rabbit and cute.
* CallBack: Emily beats D.W. and James in a swim meet, in a nod to her initial antagonistic appearance.
* GenderEqualsBreed: Both Emily and her mother are rabbits, while Emily's father is an ape.
* GratuitousFrench: She tends to use random French words and phrases from time to time, thanks to the influence of her French nanny Marie-Helene.
* SophisticatedAsHell: To a degree, as a result of her private tutoring and the fact that she's traveled to France, so she tends to act pretty cultured.
* SpoiledSweet: She's spoiled with tons of possessions, a private nanny, a tutor, and fancy food. Yet she's generally one of the nicest and most polite kids in preschool.
* TomboyAndGirlyGirl: Girly Girl to D.W.'s Tomboy. Emily tends to have more refined manners and much less of a tendency to be bossy or take a leadership role. D.W. also seems like the hardier of the two girls when it comes to roughhousing/generally dealing with the Tibble twins.
* TookALevelInKindness: Is mean to D.W. for almost all of her first appearance in "D.W. Flips". Nowadays, they're shown to be generally excellent friends.
* WiseBeyondTheirYears: Somewhat justified in that in addition to prekindergarten, she's also homeschooled by a tutor.

[[folder: James [=MacDonald=]]]
-->'''Voiced by:''' Jesse Camacho (season 8), Nicholas Wheeler-Hughes (season 11), John Flemming (seasons 16 - 17), Christian Distefano (seasons 18-present)

A shy boy in D.W.'s preschool class, and Molly's younger brother.
* BunniesForCuteness: One of the cutest rabbits in the series.
* LittleBrotherIsWatching: [[spoiler:He later starts picking up Molly's bullying behavior, prompting her to shape up so her brother won't become like her.]]
* MoralityPet: Molly's sisterly love for him influences her character. [[spoiler:When he also starts becoming a bully, Molly has a HeelRealization and tries to shape up for his sake.]]
* SiblingYinYang: A shy, kind boy who contrasts his sister Molly's tough customer act.
* TookALevelInJerkass: In S16's "The Last Tough Customer" [[spoiler:he starts adopting Molly's bullying ways and rudely shoves a young girl just to get a drink of water. Molly realizes her bad influence on her brother and vows to shape up for both of their sakes.]]
* WouldHitAGirl: [[SubvertedTrope While mimicking Molly's bullying]], Jamez pushes a girl to get water.

[[folder: Bud Tucker Compson]]
-->'''Voiced by:''' Creator/JulieLemieux

Ladonna's younger brother, and D.W.'s newest classmate. [[spoiler: The only kid in preschool who can actually cope with the Tibble Twins.]]
* ADayInTheLimelight: [[spoiler: "Bud's Knotty Problem" is Bud's first episode which doesn't give equal or greater attention to D.W.]]
* BunniesForCuteness: A rabbit who is a cute preschooler.
* DeathGlare: Normally given to the Tibble twins.
* FullNameUltimatum: Bud sometimes gets this from Ladonna.
* MrImagination: Bud's presence augments D.W.'s creativity, inspiring her wildest ideas to date.
* NeverBareheaded: 99% of the time, he keeps his hat on.
* StaringContest: Bud is undefeated; he can beat all of his siblings and [[spoiler: scare off the Tibble twins.]]
* TemptingFate: [[spoiler: In the teaser for "Bud's Knotty Problem," Bud says that there is nothing that he and D.W. can't do together. It turns out that Bud can't tie shoelaces, and D.W. can't teach him how to do it.]]
* WantingIsBetterThanHaving: [[spoiler: Bud's mom makes a deal with him, saying that she will buy him a new pair of boots with laces if he can learn how to tie them. Once Bud earns the boots, he tries them on and doesn't like them. Bud chooses a new pair of saddle shoes instead.]]

[[folder: Mei-Lin Barnes]]
-->'''Voiced by:''' Carrie Finlay

Binky's baby sister. A bear cub, she was adopted from China in season 11. She mostly appears in Kate-related episodes.
* BearyFriendly: She's a bear and a sweet one at that. However, Kate points out that Mei-Lin can be very cranky if she misses her nap.
* HappilyAdopted: By the Barnes family.
* MoralityPet: Mei-Lin's adoption has done wonders for Binky's CharacterDevelopment, even though it started way back in Season 1.

!Adult cast
[[folder: David and Jane Read]]

The parents of Arthur, D.W., and Kate.
--> '''David is voiced by:''' Bruce Dinsmore (TV series), Tony Fardella (Living Books)\\
'''Jane is voiced by:''' Sonja Ball
* AdultsAreUseless: While they're a bit less lenient with [[KarmaHoudini D.W.]] than with Arthur, they do frequently let her get away with bad things that any other parent would have disapproved of.
* AmazinglyEmbarrassingParents: They have their moments of this, like whenever Jane buys clothes for Arthur or when David insists on telling bad jokes at Parents' Night in "Kids Are From Earth, Parents Are From Pluto".
* {{Cloudcuckoolander}}: David is a downplayed example; In "Arthur Cleans Up" he is shown to easily get excited over things that he ropes Arthur in to that just leaves him feeling awkward or unsure of what he's supposed to do.
* CordonBleughChef: David likes to experiment with his cooking... with less than desired results. Arthur initially thought he was a LethalChef, but he's actually a SupremeChef... when not experimenting.
* HappilyMarried: In contrast to Buster's parents, who are divorced.
* HouseHusband: Both of the Read parents work from home. While David has his catering business, most of the money comes from Jane, who's an accountant.
* {{Keet}}: David can get very loud when he's excited or passionate about something.
* LaughingAtYourOwnJokes: Dave, usually because nobody else gets them, much to Arthur's chagrin.
* LethalChef: Played with. While Arthur initially thought this, it turns out David is actually an amazing cook. It's when he's experimenting in his cooking that the meals turn out a bit questionable. Either way, David is certainly not as bad a chef as Grandma Thora.
* NeverASelfMadeWoman: Jane straddles both sides of this trope; she shares household responsibilities with David while earning a sizable portion of her family's income, working from their home computer as an accountant. It's possible that Jane earns more money than David does.
* OOCIsSeriousBusiness: They are typically extremely ineffective disciplinarians towards D.W., but whenever they finally ''do'' punish her, you know D.W. has pushed their patience past its limit.
* ParentalObliviousness: They never seem to realize what a horribly spoiled kid D.W. is.
* SheCleansUpNicely: One episode sees Jane going downtown to do office work for a couple of weeks, and she looks great in a blouse, suit pants, and a new hairstyle.
* SupremeChef: David runs a catering business and he can make amazing meals... [[CordonBleughChef as long as he isn't experimenting]].
* WomenAreWiser: In the event that one of the couple has a lapse in focus or an emotional breakdown, Jane is more likely than David to take the lead.
--> '''Ed Crosswire''': Members of the Soccer Parents Association, I have some good news and some bad news. Trevor has decided to quit coaching soccer. \\
'''David''': Yes! Hey, maybe we could even win a game this year! \\
'''Jane''': *Whispering* David, I think that's the bad news.

[[folder: Thora Read]]
-->'''Voiced by:''' Joanna Noyes, Michael Caloz (as a child)
* CoolOldLady: She is very in tune with the times and gets along well with everyone in Arthur's gang.
* FriendToAllLivingThings: Adopts an abandoned dog named Killer who has been in and out of the pound through many owners; Thora refuses to give up on her and Killer starts a new lease on life.
* HeterosexualLifePartners: With Sarah [=MacGrady=].
* LethalChef: Notoriously so; her grandchildren do everything in their power to avoid actually eating her meals. Even David would rather that the cooking isn't left to her.
* OOCIsSeriousBusiness: If she actually tells you that she's disappointed in you, you ''know'' you've messed up.
* WomenAreWiser: Usually the voice of reason whenever Arthur, D.W., or their friends have a problem they feel they can't solve on their own.

[[folder: Oliver Frensky]]
-->'''Voiced by:''' Mark Camacho
The father of Francine and Catherine. Works as a garbage man.
* AmazinglyEmbarrassingParents: Francine imagines this in "My Dad, the Garbage Man", and she feels the need to apologize for Oliver's excessive enthusiasm in "Arthur Cleans Up".
* BewareTheNiceOnes: He's as nice as they come, but will waste no time in disciplining his daughters if he finds them doing something foolish or malicious.
* FirstNameUltimatum: When Oliver decides to test out a newly-recovered baseball-pitching machine inside the apartment, it hits the bathroom door, irritating his wife.
* FunPersonified: He's always cracking jokes, coaching sports, or having fun with his daughters.
* FurryBaldness: He has a ring of human hair around the sides and back of his head, but none on top.
* GoodParents: He's very loving and caring toward his daughters, but he won't hesitate to scold them if he needs to.
* NiceGuy: Easily one of the nicest characters on the show.
* OOCIsSeriousBusiness: However, for all that niceness, he still has his limits, and whenever he becomes stern or cross you know that Francine has messed up ''badly''.
* OneOfTheKids: He certainly has his moments, like wanting to be the first person to ride the bike that he renovated for Francine.
* WorkingClassPeopleAreMorons: Averted. Though he is a blue collar worker, Oliver is a pretty smart and nice guy, though his daughters (especially Catherine) thought he should get a more "respectable" job.

[[folder: Bitzi Baxter]]
-->'''Voiced by:''' Ellen David
The mother of Buster who is now divorced. Serves as the editor of the city newspaper.
* AlliterativeName: Her first and last name begin with B.
* TheAllegedCar: Her car, the "Baxtermobile", is a defining example of this in later seasons. Despite her lofty position as the editor of the Elwood City Times, she has yet to seek out a newer one.
* AmazinglyEmbarrassingParents: Used to be one in earlier seasons, due to her protective nature. A good example of this is in "D.W. All Wet" where she actually had a messenger send Buster his bathing cap while he was at the beach with Arthur.
* AmicableExes: With her ex-husband, Beau Baxter. [[NoodleIncident Why they divorced has never been explained]], though it's implied that it was because his job as a pilot meant he wasn't able to spend enough time with his family.
* BewareTheNiceOnes: Generally fun-loving and fair, but will not hesitate to discipline Buster if she catches him doing something foolish or dangerous.
* CharacterizationMarchesOn: Initially portrayed as overly protective of Buster, but has since become more laid back and fun loving.
* MyBelovedSmother: She dotes on Buster a lot and was once overly obsessed with his personal well-being.
* NeatFreak: A downplayed example, but Buster's sloppiness and poor manners usually justify it.
* NervousWreck: Her defining character trait in the earlier seasons, where she often frets over ''everything'' Buster does for fear of him getting sick or hurt. In later seasons though, she seems to have gotten over the worst of it.
* SecretHandshake: Shares one with Buster.

[[folder: Nigel Ratburn]]
-->'''Voiced by:''' Arthur Holden (TV series), David Kessler (Living Books)

The third grade teacher of the Arthur gang, and the primary adult character featured in the show. He is a rat, obviously.
* AmbiguouslyGay: He is single, [[Series/{{Seinfeld}} thin and neat]]. With the exception of some earlier episodes, he speaks in a somewhat "sing-songy" way compared to other adult male characters. His hobby is performing [[AllGaysLoveTheatre puppet shows]], and he owns and maintains quite a collection of marionettes.
* ADayInTheLimelight: "The Return of the King"; "The Rat Who Came to Dinner"; "Get Smart".
* BreakingBadNewsGently: "Everyone sit down, please. Mrs. [=MacGrady=] is sick. She has cancer."
* CoolTeacher: His students don't like to admit it, but his a nice guy who, while strict, is very concerned about his student's well being.
* TheDreaded: Early on in the series, he had a reputation as an in-universe MemeticPsychopath who ate nails for breakfast (without milk), was a vampire who ate children, and various other rumors. Fortunately for Arthur's class, they learned that wasn't the case, though he is a stickler for homework.
* EarlyInstallmentWeirdness: He used to be named "Emil" as seen in one flashback; this was soon after retconned to "Nigel".
* EveryoneWentToSchoolTogether: S1's "Arthur's Almost Boring Day" showcases Grandma Thora's old home movies, revealing that David Read, Mr. Ratburn, and Mr. Haney all attended the same high school at the same time. S15's "The Butler Did... What?" also reveals Bailey and Mr. Ratburn were in the same high school class.
* EvilCounterpart: The one time we get to meet his own teacher, he's shown to be a far more sadistic, cold and cruel version of Ratburn. Mr. Ratburn likely designed his teaching style off of being as work-intensive as his while being far less harsh to his students.
* FacePalm: When Muffy attributes the creation of the Dewey Decimal System to Thomas Edison.
* FormerlyFat: Once admitted to Arthur that he struggled with his weight as a kid.
* FreudianExcuse: The one occasion we encounter his mentor, who taught him everything he knows, its clear that Mr. Ratburn had to constantly work hard throughout his life to please him. His love of giving out homework most likely stems from this.
* GeniusSweetTooth: S3's "Dad's Dessert Dilemma" reveals that he LOVES cake.
-->'''Mr. Ratburn''': I just wanted of the Spring reading list-OH! Are you having cake?!?
** Would carry over in S4's "The Rat who Came to Dinner".
-->'''D.W''': There was no cake, Arthur. Mr. Rathead was very disappointed.
* HeterosexualLifePartners: With ''Arthur's dad'' of all people.
* HiddenDepths: Mr. Ratburn is often seen by the Arthur gang as a cruel teacher who has no life outside of making kids miserable. At the same time, he likes [[Franchise/ScoobyDoo Spooky Poo]], and he volunteers as a puppeteer for children's puppet shows. Oh and of course, he goes giddy over cake.
* SpeechImpediment: We find out in "Maria Speaks" that like Maria, he once suffered from a stutter in his youth.
* IWasToldThereWouldBeCake: S3's "Dad's Dessert Dilemma".
* {{Keet}}: Similar to Buster he loves eating sweets and he's a little ''too'' enthusiastic about teaching his students about subjects.
* LargeHam: He certainly has his moments of this.
* MathematiciansAnswer: [[spoiler: In " Lend Me Your Ear," Alan asks Mr. Ratburn if he wants his ice cream in a cone or a cup, to which he answers "Yes!" Alan humors him, [[TakeAThirdOption putting Mr. Ratburn's ice cream in cups and using cones as toppers]].]]
* MisunderstoodLonerWithAHeartOfGold: He doesn't have much of a social life and is feared and hated by his students for giving out homework, but he's actually a very nice and friendly guy.
* NiceGuy: He pushes his students to be the best that they can be, and won't take any nonsense from them. Overall, he's a really good guy.
* NotSoFast: When and if he does let students off the hook, he'll call for a tougher assignment to make up for it.
* NotSoDifferent: With Buster. Both love eating and cartoons. Not to mention if the high school video is any indication, he was also just like Buster as a teenager. When shown this particular video, Ratburn blushes and starts whistling innocently.
* OhCrap: In "Cents-less", he and his class go without spending money for a weekend. Unfortunately, he forgets to buy food before announcing the assignment. He puts on a puppet show to barter for some food.
* OnlySaneEmployee: While he's strict, he's the only teacher at Lakewood Elementary School who actually teaches his students properly. The only other competent employees are the lunch lady and the janitor.
* ReasonableAuthorityFigure: Despite the kids complaining about Ratburn being a Sadist Teacher, he's always looking out for their best interest and is usually the one to call out one of the kids if they're being OOC like Arthur in "So Funny I forgot to laugh".
* RunningGag: Is revealed to know nothing of the basics of a computer, and his fascination with them becomes this over the series.
* SpeciesSurname: Played straight. Guess [[RodentsOfUnusualSize what animal]] he actually is!
* SternTeacher: The kids complain about Ratburn being this. Also frequently subverted when they realize he's not that bad of a guy (just a little strict and a bit too obsessed with handing out assignments) and he's actually succeeding in teaching them things.
* TrademarkFavoriteFood: As noted above, anything to do with cake.

[[folder: Herbert/Francis Haney]]
-->'''Voiced by:''' Walter Massey

Mild-mannered, well-to-do, absent-minded bear principal of Lakewood Elementary School. Often involved in episodes taking place at the school, though he is also involved in community work.
* ButtMonkey: The early seasons often had some form of bad luck or misfortune happening to him, usually in the form of things falling on him, from raw hamburgers, to baseballs, to a bucket of popcorn, to Binky Barnes. S1's "Arthur's Almost Boring Day" reveals that he had bad luck befall him even during his school days.
* BearyFunny: His haplessness and goofy behavior gives him this.
* BearyFriendly: Very polite.
* {{Cloudcuckoolander}}: He's a pretty spacey guy.
* DeathGlare: He briefly gives Mr. Ratburn's class this when he hears them cheering ecstatically over their teacher getting sick, in a DudeNotFunny moment.
* EarlyInstallmentWeirdness: Was originally named Herbert, but his name was eventually retconned to Francis.
* EveryoneWentToSchoolTogether: Attended the same school as Mr. Read and Mr. Ratburn. Even back then, as shown in the old videos in S1's "Arthur's Almost Boring Day", he had bad luck.
* InconsistentColoring: Animated with more of a greenish color starting in season sixteen.
* LIsForDyslexia: Shortly after George finds out that he has Dyslexia, Mr. Haney is also revealed to have it. This gives them something to bond over.
* PutOnABus: [[spoiler: Leaves to build a school in Tanzania in "The Hallway Minotaur."]]
* ReasonableAuthorityFigure: Generally manages the school quite well and gets along well with all of the students and staff, and when the situation demands it will take the necessary action needed to keep things running smoothly.
* RunningGag: As noted above, he was very accustomed to having things dropped on him or having all manners of bad luck cramp his day, usually followed by the kids uttering "Sorry, Sir". As of later seasons, he seems to have caught a break.
* UnwittingInstigatorOfDoom: He entrusted his tax returns to Arthur without telling him anything about what the contents of the envelope were, and Arthur frets so much over what's in it that he very nearly throws them out instead of delivering them to his mother as promised.
* TheVoiceless: Became this after the 2014 death of his voice actor.

[[folder: Sarah [=MacGrady=]]]
-->'''Voiced by:''' Bronwen Mantel

The cafeteria lady at Lakewood Elementary.

* ADayInTheLimelight: ''The Great [=MacGrady=]'', where she is diagnosed with cancer and forced to take a leave of absence while she undergoes treatment. All the children do what they can to support her until she's well enough to return to work.
* CoolOldLady: She's very streetsmart and is well-liked by everybody at school.
* HeterosexualLifePartners: With Thora Read.
* NiceGirl: She's a very good natured person who is always willing to help those who need it.
* SecretTestOfCharacter: Performs one of these on the kids in "Draw!" when they draw a bunch of unflattering comics about Francine after she insults Fern. She tricks the kids into thinking they'll get back at Francine by dumping slime on her, but moves Francine to express how hurt she is by their teasing which moves the rest of the gang not to go through with their prank. Everybody quickly reconciles thanks to this.
* SupremeChef: Played with; there are several episodes where the students are served questionable meals, but Mrs. [=MacGrady=] is generally shown to be an excellent cook.
* UnwittingInstigatorOfDoom: In "Arthur Accused" she absentmindedly bakes quarters earned for a school charity into a batch of brownie mix, which lands Arthur in hot water as he was to make sure she got them. Buster eventually uncovers this mistake, and so she's much more careful as a result.
* WomenAreWiser: She has plenty of old school philosophies that have helped the children to overcome the questions and problems they face.

[[folder: Edward Edsel "Ed" Crosswire]]
-->'''Voiced by:''' A.J. Henderson

Used-car salesman who is Muffy's father and somehow independently wealthy.

* ADayInTheLimelight: Despite (and perhaps due to) hinging on the kind of lesson that never seems to stick for Muffy, with Ed elbowing his way in on Muffy's class project, "Muffy Takes the Wheel" arguably has more to do with his character development than hers.
* GoodParents: While he spoils his daughter rotten, he clearly loves her deeply and is very worried about her happiness.
* HonestCorporateExecutive: He's always trying to find new ways to sell his products, but he never makes false promises.
* HonestJohnsDealership: Subverted. He's not into false advertising, but is very...assertive when it comes to selling cars.
* MeaningfulName:
** An Edsel was a type of car made by Ford known as a commercial failure, but one of the meanings of the name itself is "rich."
** "Crosswire." As in hotwiring a car. It can also mean "crossed wires", as in RichInDollarsPoorInSense. It fits for his whole family.
* NonIdleRich: He's a used-car salesman and clearly takes his job seriously, despite the pampered princess life he gives his daughter.
* NouveauRiche
* RepetitiveName: His first name is Edward and his middle name is Edsel.
* SelfMadeMan
* WellIntentionedExtremist: Once tried to convince both the parents and the library that scary books were bad for children when Muffy supposedly suffered nightmares from them, going so far as to push the library to pull such books from circulation. After actually sitting down to hear one of them read and realizing Muffy actually enjoyed them as well, he has a change of heart.
-->'''Voiced by:''' Simon Peacock, Michael Yarmush (during an ImagineSpot in "Sick As A Dog"), Arthur Holden ("And Now Let's Talk To Some Kids"), Yvette Kaplan (''Arthur's Missing Pal'')
Arthur's dog and the best friend of Kate in the episodes focusing on them.
* AnimalTalk: He can talk to other animals and [[SpeaksFluentAnimal Kate]].
* BlackBeadEyes: Beady dot eyes.
* ConspicuouslyLightPatch: Thanks to this, we know which of Perky's puppies he is.
* OralFixation: As a puppy he would bite on a lot of things, such as his leash.
* PreciousPuppies: He isn't an actual puppy, but still adorable nonetheless.
* SickEpisode: "Sick As A Dog" revolves around him being ill after sampling one piece of human food too many.
* TrademarkFavoriteFood: He loves his bacon.
* TroublemakingNewPet: When he was a puppy he was rambunctious and wouldn't always listen to Arthur.
* WhyDidItHaveToBeSnakes: He's afraid of cats.
-->'''Voiced by:''' Greg Kramer
Francine's cat. He's the enemy of Kate and Pal.
* AnimalTalk: He can speak to other animals and Kate.
* CatsAreMean: He's a cat who's a condescending snob.
* ChuckCunninghamSyndrome: He made a cameo after his voice actor passed away in 2013, but hasn't appeared since.
* EarlyInstallmentCharacterDesignDifference: Had a much different appearance in his debut episode.
* PlotAllergy: [[{{Irony}} Nemo is allergic to milk]].
* IronicFear: [[spoiler: He's terrified of Ladonna's pet rat, General Higgins]].
* TheRival: To Kate and Pal.
* TookALevelInJerkass: Contrary to Arthur's objections, he was shown to get along with Pal upon his debut in "Francine and the Feline". For unexplained reasons, they afterward became bitter enemies.
-->'''Voiced by:''' Melissa Pirrera
Grandma Thora's pet Jack Russel terrier.
* AnimalTalk: She can speak to other animals and Kate.
* CanonImmigrant: She first appeared in the book ''Arthur's Christmas'' before making her animated debut in Season Nine's "It Came From Beyond".