Arnold Phillip Shortman (voiced by Toran Caudell in season 1, Phillip Van Dyke in seasons 2–3, Spencer Klein in seasons 4–5 and Hey Arnold!: The Movie, Alex D. Linz in the post-movie episodes, and Mason Vale Cotton in Hey Arnold!: The Jungle Movie), is the nice, kind, optimistic nine-year-old protagonist and title character of the series. He is a dreamer and an idealist who always tries to see the best in people and do the right thing. His parents, Miles and Stella left to go to San Lorenzo when he was 1 year old, but never came back to Hillwood. Whenever he sees someone in trouble, especially Helga, Arnold goes out of his way to help them out, even if it is not sensible to do so. Arnold often acts as the stable center to those around him, whether he is around his "family" in his paternal grandparents' boarding house, or around his friends at school. He lives in Sunset Arms boarding house with his grandparents, Phil and Getrude.
Arnold has had two major crushes in the series: one with sixth-grader Ruth McDougal (through most of season 1), and one with a classmate named Lila Sawyer (from season 2 onwards). However, his most catalytic relationship is with his classmate and friend Helga Pataki. Helga is secretly in love with him, though to keep these feelings secret she bullies Arnold. Arnold is completely unaware of this fact for most of the series, other than the occasional hint from Helga and other classmates. Helga revealed her secret to Arnold during Hey Arnold!: The Movie, but Arnold gave Helga the opportunity to take back her confession, attributing it to "the heat of the moment". According to series creator Craig Bartlett, had the canceled "Jungle Movie" sequel been animated, Arnold would have returned Helga's feelings with a kiss of his own, with his best friend interrupting the moment. Arnold is friends with most of his fellow fourth-graders, with the best of which being Gerald Johanssen, whose friendship dates as far back as preschool.
Arnold's surname is never revealed on the show and the mystery surrounding his full name became a running gag on the show, by the last name almost being revealed, then someone or something interrupting or otherwise preventing it from being heard. It was finally revealed that his full name was Arnold Phillip Shortman.
Gerald Martin Johanssen (voiced by Jamil Walker Smith throughout the original series and Benjamin Flores, Jr. in Hey Arnold!: The Jungle Movie) is a nine-year-old boy and Arnold's best friend. He is an athletic and street-smart boy who is portrayed as loyal, though much less responsible than Arnold. Gerald has known Arnold for many years, most likely since preschool. Besides being Arnold's friend, Gerald also has a good deal of knowledge of many legendary stories in the city, or "urban legends" as he calls them. He apparently gets these myths from a source he has nicknamed "Fuzzy Slippers", mentioned in many episodes as his reliable assistant.
At school, Gerald is the class president, and considers himself very cool, and apparently, so do his friends. When it was revealed that Arnold was on Rhonda's so-called "Cool List", and that Gerald was on her other list known as "The Geek List" (due to a grudge Rhonda had against him over running for class president), many classmates were surprised to find this out ("Cool Party").
His most distinct features are his tall, Kid 'n Play-style hair, and his shirt with the number 33 on it (he also wears 33 on sports uniforms). He has a crush on Phoebe, who shares the same feelings for him.
"Arnold this is the life, not going to school, drinkin yahoo sodas, and wearing beards."
Helga G. Pataki (voiced by Francesca Marie Smith) is a rough and cynical girl who puts on a mean, tomboyish front, making her the fourth grade bully. She constantly bullies Arnold to hide her true feelings of love for him, which is obsessive to the point where she has made many shrines dedicated to him. She is an academically-gifted student and a talented writer of poetry for her age. She occasionally expresses interest in pursuing the latter as a career. Despite this, she is neglected by her parents and often disrespectively calls them by their first names because she does not think they are worthy of being called "Mom" and "Dad". Her alcoholic mother, Miriam, is usually depressed, forgetful, struggling to stay conscious, and frequently drinking "smoothies" and "coffee". Helga relates very poorly to her. Her father, Bob, a successful pager salesman, who suffers from workaholism, rarely notices her existence, favoring her over-achieving, neurotic college-aged sister Olga, who Helga rarely gets along with. Helga does not really see him as her father, seeing as he is a horrible one. He never listens to Helga. Helga is also known for her catchword, "criminy", which she normally exclaims when stressed.
Helga resents her older sister Olga, a perfectionist. Once in a while, Helga will show a very small amount of love for her sister, as in the episode "Olga Gets Engaged", when she intervenes on Olga's behalf, saving her from what would have been a bad marriage, and "Big Sis" when she reveals her jealousy of Olga's relationship with Lila. Although Helga will do her best to avoid unnecessary contact with Olga, she has shown feeling of love for her sister from time to time.
Phoebe Heyerdahl (voiced by Anndi McAfee) – The smartest girl in Arnold's class. She is Helga's best friend and confidante, though Helga tends to boss her around. Nevertheless, Phoebe acts sometimes as Helga's moral compass, advising her on what she should do. Her ethnicity is half-Japanese, but she is from Kentucky. Being the smartest girl in her class is very important for her, and she tries her hardest to be that way. Throughout the series, both she and Gerald have a love interest in one another.
Harold Berman (voiced by Justin Shenkarow) – A Jewish American student and friend of Arnold. Although he was portrayed in the first season as an antagonist who frequently picked on Arnold, he became more of a companion to him later on as the role of school bully increasingly shifted over to Wolfgang. Despite his frequent bullying and intimidation of other students, Harold's bullying is generally verbal rather than physical and he is often revealed to be rather cowardly and usually cries for his mother whenever he gets scared or upset. He is sometimes referred to by the derisive nickname "fat boy", usually by Helga. He is 13 years old and overweight and in later episodes it is revealed that Harold has a soft spot. His best friends are Sid and Stinky.
Stinky Peterson (sometimes spelled Petersen) (voiced by Christopher Walberg in the series, Jet Jurgensmeyer in The Jungle Movie) – Stinky is a tall and lanky friend of Arnold's whose family is from Arkansas, and he is also one of Harold's best friends. Stinky has a Southern accent and a love for lemon pudding. His friendship with Harold had him originally portrayed in the first season as a bully who wore spiked wristbands and sidekick of Harold's, though the former was later de-emphasized and he was reinvented as a more affectionate, mild mannered and romantic character viewed as the class "ladies man", as he is romantically attracted to several female characters. He is shown to make up excellent poems while Phoebe is feeling depressed.
Sid (voiced by Sam Gifaldi in most episodes, Taylor Gifaldi in "April Fool's Day", and Aiden Lewandowski in The Jungle Movie) – A friend of Arnold and one of Harold's best friends with paranoid tendencies. He is always shown wearing a green baseball cap backwards, a black leather jacket, and white Beatle boots. He often tells urban legends, with or without the assistance of Gerald. Perhaps his most well-known characteristic is that he typically ends up in ridiculous situations, such as becoming severely mysophobic; deciding to devote his life to Arnold after Arnold saves his life, among other things.
Rhonda Wellington Lloyd (voiced by Olivia Hack) – A rich, pompous, self-proclaimed fashion queen and friend of Arnold. She is one of the most popular students attending P.S. 118. Both of her parents are stereotypically preppy. Even though she is always seen concerned about her style, Rhonda is a phenomenal athlete, practicing numerous contact sports, like baseball and football, not caring if she ruins her clothes or accessories.
Eugene Horowitz (voiced by Christopher Castile, then Jarrett Lennon in season 1, then Benjamin Diskin for seasons 2-4, Blake McIver Ewing in season 5 and the movie and Gavin Lewis in The Jungle Movie) – A somewhat socially inept but optimistic friend of Arnold, the class jinx. Eugene is prone to several forms of misfortune and is often bullied. He believes Arnold is a jinx due to several of his past tragedies having occurred in Arnold's presence.
Lila Sawyer (voiced by Ashley Buccille) – A nice girl who came from a fictional farming community she calls "Pleasantville" and who lives with her father. Her mother is never seen or mentioned. She is Arnold's crush. However, she only prefers Arnold as a friend. She had a crush on Arnold's cousin Arnie. She knows that Helga loves Arnold and offered to help Helga become more like her in one episode. She is described by the show's creator as being a foil for Helga and as having a sort of twisted darkness hidden beneath her kind exterior.
Oskar Kokoshka (voiced by Steve Viksten in the series and theatrical film, Wally Wingert in The Jungle Movie) – A lazy, selfish, inconsiderate, insecure immigrant from an Eastern European country (in one episode he is referred to as being Czechoslovakian), that remains unemployed through most of the series, until becoming a paperboy. He has a gambling problem, doesn't do what he promised, and is a pathological liar, even lying to kids like Arnold who often tries to help him out. His childish demeanor and whininess often irritate others. Despite all his negative, despicable personality traits, he does love his wife and feels really bad when he thinks he has let somebody down. His voice resembles that of comedian Yakov Smirnoff and he occasionally utters Smirnoff's catchphrases. He shares his name with an Austrian artist.
Suzie Kokoshka (voiced by Mary Scheer) – Oscar's hard-working, dedicated, mature, loving and caring wife, who puts up with all of her husband's antics, selfishness, and laziness, though the two occasionally fight.
Ernie Potts (voiced by Dom Irrera) – A short-statured and hot-headed, demolitionist who has a Napoleon complex.
Mr. Hyunh (voiced by Baoan Coleman in the original series and also Wally Wingert in Hey Arnold!: The Jungle Movie) – His last name (a misspelling of Huỳnh) is pronounced "win." He is an immigrant from Vietnam, working in a Mexican restaurant. Despite having a heavy Vietnamese accent when speaking, it is revealed that he is very talented in singing country music with the singing voice provided by country singer Randy Travis. He can also play cello, guitar and trumpet quite well. His wife is never seen or mentioned. One episode reveals that he has a long lost daughter, but that he asked a US soldier to take her out of the country to avoid the Vietnam War. They are reunited years later.
Mr. Smith – A mysterious character who lived in the boarding house. Very secretive. His face is never seen, nor his voice has ever been heard. He is resented by the other boarders, due to this secretive lifestyle, as he doesn't share many of the main boarding house facilities, which are limited, based on the number who live there. He only appears in the first season.
Lana Vail (voiced by Christine Ebersole) – A lawyer who resides in the boarding house. She wears a purple suit and has brown hair. She was a minor character to begin with, and has brief appearances throughout the series. She has Her only speaking appearance in "Heat".
Mr. Purdy (voiced by Joseph Purdy) – he is only mentioned once in the episode "Gerald Comes Over" when Arnold collects the rent money. There are suspicions of him sharing his room with a chicken, this from chicken noises as Gerald listens from outside his door, never revealed, but covered up by him.
Grandpa Phillip or Phil (voiced by Dan Castellaneta) – Arnold's cheery, fun-loving grandfather. He is 81 years old, as of the episode "Grandpa's Birthday". Arnold often comes to him for advice. He often tells Arnold stories about his past experiences, although he has a tendency to stretch the truth. Despite responding frivolously to Arnold's problems, he will often provide good wisdom. While his advice is not usually the most helpful, his heart is always in the right place. He is a World War II veteran and claims to have single-handedly won the Battle of the Bulge by tricking a large troupe of Nazi soldiers into eating numerous cans of spoiled CHAM (a spoof of Spam), thereby poisoning them and creating a hole in the enemy line for the American troops to break through. Arnold does not believe his story at first, but it is later proven when Phil shows him a small monument of him hidden in some bushes in a park in Washington D.C. Phil was also a master at Chinese checkers in his youth, which earned him the nickname "Steely Phil". He is very healthy and spry for his age, as well as athletic.
Grandma Gertrude (voiced by Tress MacNeille) – Arnold's wacky but wise grandma who is often seen doing outlandish things, including dressing up and acting like fictional and historic figures, such as Calamity Jane. She is called "Pookie" by Grandpa Phil and Gertie by Aunt Mitzi She has a black belt. She and Phil had a similar relationship that Helga and Arnold have when they were kids (though her antics were a bit more vicious and extreme).
Arnie (voiced by Grant Hoover) – Arnold's cousin, who lives in the countryside and strongly resembles Arnold. He likes to collect lint and gum, count things, read the ingredients on the back of food containers, and makes a peculiar snorting sound on occasion. When he visits PS. 118, Lila develops a crush on him and attempts to attract his attention, but he develops an unrequited crush on Helga. He is often seen as strange, gross, dull or stupid by those around him.
Miles and Stella (voiced by Craig Bartlett and Antoinette Stella) – Arnold's parents, Miles being Phil and Gertrude's son. They are adventurous and brave, though Miles appears to be clumsy and tends to end up hurt. They met while exploring in San Lorenzo, where they occasionally crossed paths with the Green-Eyed people, a mysterious indigenous tribe. They returned to the city after Arnold's birth, but were called back for 'a final mission' when a friend informed them that the Green Eyes were in trouble: they failed to return, leaving their son under his grandparents' care. Arnold comes across a journal detailing some of their adventures years afterwards. His pet pig, Abner, was a wedding gift to his parents from the Green Eyes.
Aunt Mitzi (voiced by Phyllis Diller) – Arnold's great aunt, Phil's twin sister and childhood rival. She is 81 years old.
Grandpa Phil's father (voiced by Dan Castellaneta) – He is often seen in Grandpa's flashbacks to the 1920s.
Grandpa Phil's grandfather (voiced by Dan Castellaneta) – He is seen in one of Grandpa's flashbacks. Grandpa remembers doing chores one winter while his friends were ice skating, only to be hit with a snowball by his grandfather who gave him permission to stop his chores and play.
Robert "Big Bob" Pataki (voiced by Maurice LaMarche) – Olga and Helga's oafish, ambitious entrepreneur father, a successful beeper salesman who owns a beeper store. He has extremely high expectations for Helga and frequently compares her to her older sister Olga. Bob also frequently calls Helga by Olga's name by mistake. However, Bob does care for Helga as is evidenced in subtle ways. Bob has difficulty showing his emotions for Helga since she and he always come into conflict with each other. He often mistakenly calls Arnold "Alfred".
Miriam Pataki (voiced by Kath Soucie) – Olga and Helga's inattentive mother. It is hinted throughout the show that Miriam suffers from alcoholism, as she often drinks "smoothies" which sometimes contain ingredients found in alcoholic cocktails such as celery and tabasco sauce, forgets things, speaks in a slow, tired voice, has had her driver's license revoked, has to do community service and sleeps a lot (often in inappropriate places). Like Bob, it is shown in very subtle ways that she cares about Helga, such as checking in her room when she heard a crash. The unaired Hey Arnold! spin-off, The Patakis, would have included her struggle with alcoholism and joining of Alcoholics Anonymous as a plot point. However, in one episode when Bob injures his back and can't work, Miriam fills in for him. During the episode Miriam sobers up and holds the fort. Miriam also becomes more attentive towards Helga until she becomes a workaholic and realizes that she is ignoring Helga. Then, she quits and makes Bob return to work. However, her sobriety doesn't last long because in episodes following this one, she is back to drinking smoothies. Miriam was a champion bull rider before marrying Bob, and she used to be an Olympic class swimmer. She reveals in the episode "Olga Gets Engaged" that she regrets marrying Bob, which resulted in throwing her life away and presumably resulting in her insecurities.
Olga Pataki (voiced by Nika Futterman) – Helga's intelligent, outgoing, beautiful older sister, who attends the fictional Wellington College. But in one of the episodes, Helga says that Olga attends Bennington College, which is an existing college located in the U.S. state of Vermont. Olga clearly suffers from perfectionism. She possesses skills that demonstrate a high-level of intelligence such as in the episode "Helga on the Couch", where she was shown to be a virtuoso pianist in one of Helga's flashbacks, and when Helga mentioned that she was a straight A student. She attended P.S. 118 as a child, and is praised by Helga's current teachers for her achievement. Bob and Miriam consider Olga to be perfect, which bothers Helga. There are times where her parents will confuse Helga for Olga. Fortunately, Olga does give Helga more attention than their parents much of the time and has good intentions. However, Helga does not receive Olga's attention or intentions very well and often tries to push Olga away and keep her distance. Olga has a tendency to view life through rose colored glasses and appears not to notice Helga's avoidance tactics. Therefore, either Olga likes to avoid conflict since she rarely acknowledges her family's problems, is oblivious, or is in denial. It is revealed in the episode "Helga on the Couch" that Olga through the years has reacted to her family's problems by being a perfectionist and keeping quiet about the situations at hand. She later reveals to Helga that she is envious of her, as unlike Olga, their parents never heaped unrealistic expectations onto her, comparing herself to a "wind-up toy" that performs for their parents.
Martin Johanssen (voiced by Rick Fitts) – Gerald's sometimes strict father, complains about wasting electricity. He is a Vietnam War veteran.
Mrs. Johanssen (voiced by Shari Belafonte) – Gerald's very kind mother, keeps family together. She is a cashier at the neighbourhood market.
James "Jamie O" Johanssen (voiced by Ben Aaron Hoag and Phil LaMarr) – Gerald's older brother, who causes trouble for him.
Timberly Johanssen (voiced by Avriel Epps and Francesca Smith) – Gerald's little sister. She usually causes trouble due to her desire for attention or naturally childish behaviour. Unlike all the other children on the show, Timberly seems to age throughout the series. In her first appearance, she is four years old, but she already attends the first grade in "Timberly Loves Arnold", although this may be a continuity error, rather than intentional.
Kyo Heyerdahl (voiced by George Takei) – Phoebe's Japanese American father. Speaks Japanese fluently. However, his surname is not Japanese.
Reba Heyerdahl (voiced by Jean Smart) – Phoebe's Southern American mother from Kentucky (possibly based on Reba McEntire).
Jerry Berman (voiced by David Wohl) – Harold's father. He has a tendency of talking in a very low pitch, and is more concerned about Harold's obesity than his wife.
Marilyn Berman (voiced by Kath Soucie) – Harold's mother. She is more vocal with her scolding of Harold than her husband.
Nate Horowitz (voiced by Michael Jeter) – Eugene's father. He is equally unlucky as his son as seen in the episode "Fishing Trip".
Mrs. Horowitz – Eugene's mother (only appears in the episodes "Eugene's Birthday" and "Parents' Day" )
Brooke Lloyd (voiced by Lori Alan) – Rhonda's mother who believes her daughter is a perfect angel who can do no wrong.
Buckley Lloyd (voiced by Sam McMurray) – Rhonda's father.
Lila's father (voiced by Dan Butler) – Lila's father is seen in the episode "Ms. Perfect". He appears to be a kind and caring father. When Lila is new to P.S. 118 and being bullied by some of her classmates, her father tries to be there for her. In the episode it is revealed that he had been unemployed and it ends happily with him getting a job.
Thaddeus "Curly" Gammelthorpe (voiced by Adam Wylie in most episodes, Haley Joel Osment in "Deconstrucing Arnold" and Michael Welch in "Ghost Bride" and "Curly's Girl", Nicolas Cantu in The Jungle Movie) – The class psychopath. He has had meltdowns and outbursts throughout the show such as in the episodes "False Alarm" and "Curly Snaps". He also appears to have a major crush on Rhonda. In the episode "Curly's Girl", Rhonda pretends to be Curly's girlfriend for a week, but she is disgusted by his appeal.
Torvald (voiced by Michael Bacall) – A fourth grader who was held back for several years due to his poor math performance (to the point of not knowing the answer to 3x3) and is considerably older than the rest of the students. He is tutored by Arnold in one episode. In the episode "Tutoring Torvald", he is revealed to be 13 years old.
Sheena (voiced by Francesca Smith) – A geeky girl who does not like violence. Her aunt Shelly is the school nurse, her uncle Earl rows a boat.
Lorenzo (voiced by Victor Samuel Lopez) – A wealthy Hispanic American boy who did not have enough time to be a kid, by his mother's schedule. Arnold and the other kids teach him what it means to be a kid.
Iggy (voiced by Justin Shenkarow in "Downtown as Fruits", Sam Gifaldi in "Heat", Marcus Toji in "Stoop Kid" and Joseph Ashton in "Arnold Betrays Iggy" and "Gerald's Game") – A friend of Arnold's who was popular until his classmates found out he wears bunny pajamas in "Arnold Betrays Iggy". During the first season, he was shown as something of a troublemaker who would sometimes co-operate with Harold in mischievous deeds. His shirt tails stick out like Arnold's, creating illusion of a kilt. Iggy almost always wears dark sunglasses that he rarely takes off.
Brainy (voiced by Craig Bartlett) – A geek and Helga's stalker who is usually knocked unconscious by Helga without Helga looking at him. He seems to be romantically attracted to her. He has a very deep voice, wheezes noisily, and never talks in a completed sentence. He rarely appears except when Helga looks at her locket containing a picture of Arnold. Apparently Brainy has not told anybody else about Helga's crush on Arnold.
Nadine (voiced by Lauren Robinson in the series, Laya Hayes in The Jungle Movie) – A young entomologist and Rhonda's best friend. She tends to find a lot of Rhonda's more stuck up opinions ridiculous. In the episode "Dinner for Four", she sets cockroaches free in a restaurant as a favour for Helga. This is the only episode where she has a bigger role than Rhonda, for her usual role is Rhonda's satellite character. In "Parents Day", Nadine is shown to be half black and half white.
Park (voiced by Marcus Toji) – A close friend of Arnold and others. In the episode "Longest Monday", it is revealed he has a secret hideout. He only speaks in seasons 1–3.
Joey Stevenson (voiced by Justin Shenkarow in earlier appearances, Michael Fishman in later appearances) – An African American boy who is easy to remember by knowing he is missing a tooth. He appears with Arnold's group of friends from time to time, though his most prominent roles are in the first season, when he was part of Harold's circle of friends, along with Iggy, Stinky, and Sid.
"Chocolate Boy" (voiced by Jordan Warkol) – A boy obsessed with chocolate. In "Chocolate Boy", it is revealed he eats chocolate because his nanny fed him large amounts of chocolate before she left to a "far away land called Delaware." Arnold helps break Chocolate Boy of his obsession, but he only becomes as equally over-excessive eating radishes as a replacement.
Wolfgang (voiced by Toran Caudell) – The main bully of the block who is a fifth grader and Arnold's nemesis. He also runs the fifth grade and leads the other fifth grade bullies in their troublemaking against younger students. Similar to Arnold, Wolfgang is somewhat popular with many friends in his grade level, the best of which being his right-hand man, Edmund.
Edmund (voiced by Tim Wiley) – Wolfgang's best friend and sidekick. He often asks stupid questions, causing Wolfgang to remark "Shut up, Edmund."
Mickey (voiced by Marty York) – A fifth grader who is nicknamed "The Weasel" as seen in "Longest Monday."
Gloria (voiced by Francesca Smith) – A girl who looks like Helga, but is more girly and has a nicer personality. Her first appearance is in "Magic Show" as a dream vision, but she is revealed to be a reality in "Helga's Boyfriend" when Stinky begins dating her, and appears as an extra in "Cool Party".
Ludwig (voiced by Phillip Van Dyke) – A bully who was Wolfgang's rival and is later Wolfgang's friend. His name is likely a reference to Ludwig Van Beethoven, a famous classical composer, as a counterpoint to Wolfgang who shares his first name with classical composer Wolfgang Amadeus Mozart.
Ruth P. McDougal (voiced by Lacey Chabert) – A sixth grade girl who is Arnold's first crush.
Connie and Maria (voiced by Pamela Hayden and Mayim Bialik) – Two sixth grade girls, Maria is a Latina, who speaks with that accent, often using Spanish words in discussion. They ask Arnold and Gerald to be their dates in "dates" although just to use them to make their boyfriends jealous, but both agree that they are sweet and have potential to attract their interest in the future, when they are older than fourth graders. The two often appear in later episodes when the sixth grade classroom is shown, either with or without dialogue. In "Phoebe Skips", their character is more of an antagonist, taking advantage of Phoebe's brains, while in "Back to School" they plan to sneak into a PG 13 movie, with Arnold's grandpa.
Patricia "Big Patty" Smith (voiced by Danielle Judovits) – An ill-tempered sixth grade girl who becomes Harold's friend (it is implied that the two may have romantic feelings for each other as well). She beats up Helga when she falls victim to her pranks (originally intended for Lila). In a later episode, she plans to fight Helga, but stages it instead. She even asks Helga if she and Arnold had feelings for each other, which Helga denies. In season 4, she becomes friends with Rhonda after they both attend the same finishing school together. She was also held back a couple of years and is 14 years old.
Patty's mother (voiced by Zelda Rubinstein) – Mother of Patty who possess the medical condition of dwarfism.
Patty's father (voiced by Henry Gibson) – Father of Patty who also possesses the medical condition of dwarfism.
Superintendent Chaplin (voiced by Jack Angel) – An official who supervises schools in the city as seen in "Principal Simmons".
Principal Wartz (voiced by David Wohl) – The strict, yet open-hearted principal of the school.
Dr. Bliss (voiced by Kathy Baker) – A child psychologist who evaluates the students of P.S. 118 for a day and later becomes Helga's psychoanalyst. Also the second known character that is told by Helga that she loves Arnold. This character only appeared in one episode titled "Helga on the Couch."
Miss Felter (voiced by Julia Louis-Dreyfus) – A substitute teacher who was one of Arnold's "crushes." This character only appeared in the episode "Crush on Teacher."
Mr. Frank – A sixth-grade teacher, who is quite bored with his job.
Lieutenant Major Goose (voiced by John Garry) – Arnold's teacher for short time (after Miss Slovak and before Mr. Simmons), a martinet. He also was Martin Johanssen's drill sergeant during Vietnam War flashbacks in "Veterans Day" episode.
Lunch lady (voiced by Kath E. Soucie and Danica Ivancevic) – A woman in charge of the school cafeteria. She is stereotypically brash in appearance, but sensitive to criticism of the cafeteria food.
Mr. Packenham (voiced by Daniel Stern) – A fifth grade teacher. He appears in "What's Opera, Arnold?" when he chaperons Arnold's class trip to the Opera and in "Back to school" when Arnold's grandpa returns to school for a grade school diploma, while in fifth grade, during rapid progress from fourth through to sixth grade.
Miss Slovak (voiced by Tress MacNeille) – Arnold's enthusiastic teacher (in the first season and part of the second season). She leaves teaching to pursue a career in golf.
Mr. Robert Simmons (voiced by Dan Butler) – Arnold's sensitive and caring teacher (since the second season). He replaced Miss Slovak. He emphasizes the unique value of every individual in his class, with his constant reminding that "you are all special in your own special way".
Shelly (voiced by Mary Gross) – The school nurse, and Sheena's Aunt
Coach Jack Wittenberg (voiced by James Belushi), the competitive school coach of many sports teams, which he often gets Arnold and his friends to join. He is portrayed as an aggressive and incompetent coach, unable to motivate and guide his team properly. With Arnold's help, he is able to lead his team to victory, as in the episode "Synchronized Swimming", and is revealed to have a sensitive and considerate side. He has poor vocabulary, often mispronounces words, while confidently verbose.Tish Wittenberg (voiced by Cathy Moriarty) – Jack's wife who is the coach of girls' teams. She and Jack often compete with one another.
Tucker Wittenberg (voiced by Grant Gelt) – Jack's son who is a student of PS 118.
Rex Smythe-Higgins (voiced by Tony Jay) – Grandpa's archrival from when he was a child, of an esteemed British family, and often shown to have cheated against him in the past
Rex Smythe-Higgins III (voiced by Joey Stinson) – His grandson, and similarly a rival to Arnold. However, unlike their grandfathers', the two have a respect for each other as they shook hands following Arnold winning a boat race which Rex refused to cheat in, and Rex even siding and helping Arnold save his pig Abner when his grandfather wanted to eat it.
Dino Spumoni (voiced by Rick Corso in the original series and Wally Wingert in Hey Arnold!: The Jungle Movie) - A famous jazz singer loosely based on the late Frank Sinatra.
Don Reynolds (voiced by Harvey Korman) - Dino Spumoni's estranged, bitter partner and songwriter.
Mr. Bailey (voiced by Vincent Schiavelli) – A worker of the Hall of Records. His first appearance is in the Christmas special, where Arnold comes to him to help find Mr. Hyunh's daughter, Mai. His second appearance is in the series' feature film, where he helps in trying to find the document of the "Tomato Incident". When he can't find it, he tells Arnold about a man who keeps all kinds of historic records.
Mayor Dixie (voiced by Tress MacNeille) – The female mayor of Hillwood. In Hey Arnold!: The Movie, she allows Scheck to redevelop Arnold's neighborhood, even though the city council rejected the idea. When she is shown Scheck destroying the document of the "Tomato Incident", she decides to make it a historic landmark once again.
Mrs. Vitello (voiced by Elizabeth Ashley and Kath E. Soucie) – The owner of the neighborhood flower shop.
Councilman Marty Green (voiced by James Keane) – a dedicated butcher and a politician who works at Green Meats. He has two brothers, Dave and Benji, and a son who is a vegetarian.
Earl (voiced by Dan Castellaneta and Craig Bartlett) – He runs a passenger ferrying service across the lake to Elk Island, in a row boat. Despite his profession, he reveals that he can't swin in the episode "Busses Bikes and Subways" He speaks with a suitable pirate accent, given his job, as well as other pirate stereotypes. He's also Sheena's uncle.
Davy Jones (voiced by himself) – Former member of The Monkees.
Mickey Kaline (voiced by Ron Perlman) – A retired baseball star and Arnold's favorite player. Arnold caught his final home run ball. After retirement he ran his own baseball-themed restaurant, Mickey's Dog Pound. He is based on two famous baseball players, Mickey Mantle and Al Kaline.
Jimmy Kafka (voiced by Richard Mulligan) – Phil's best friend when they were young kids. Phil often mentions him when he tells Arnold stories of his past exploits. They both have had a bittersweet relationship, based on many disagreements involving competitions and other activities, however deep down they are very close, despite possible continuity errors following season 1's "Part Time Friend's" episode in which it is said that he has not spoken to him since falling out working together.
Rabbi Goldberg (voiced by Elliott Gould) – A rabbi who gives Harold advice and guidance. In "Harold the Butcher", Rabbi Goldberg teaches Harold that stealing is wrong, and in "Harold's Bar Mitzvah", Goldberg helps Harold prepare for his Bar Mitzvah.
Alphonse Perrier du von Scheck (voiced by Paul Sorvino) – A greedy developer who plans to tear down the neighborhood so he can build a mall, but is thwarted by Arnold, Helga, and Gerald. He serves as the main antagonist of Hey Arnold!: The Movie.
Nick Vermicelli (voiced by Dan Castellaneta) - One of Big Bob's business associates, and later an accomplice of Scheck. He serves as the secondary antagonist of Hey Arnold!: The Movie.
Big Gino (voiced by Cameron Van Hoy) – The school's mafia boss and loan shark, often shown victimizing students, particularly Sid in "Big Gino" with harassment and threats, when they fail to pay back on time what is loaned. Though often seen in or around P.S 118, he attends P.S 119. Despite his name, due to the irony of his small stature, it is his nickname.
Stoop Kid (voiced by Danny Cooksey) – A teenage kid who lives on a stoop and never leaves it until episode "Stoop Kid", when Arnold coaxes Stoop Kid to finally have the courage to leave his stoop. The only other times Stoop Kid is seen off of his stoop are in the episodes "Arnold Betrays Iggy", where Stoop Kid is seen in the crowd of people near the end of the episode, "Eugene, Eugene!", when he is seen in the audience during the school's musical, and "Cool Party" when he is a guest at Arnold's 'geek' party.
Campfire Lass (voiced by Francesca Marie Smith) – A young girl who is the head of a junior survivor skills based troop, called the Campfire Lads. She speaks with a Scottish accent, though Arnold thinks it is fake, and is often seen selling various goods to raise money for outings, or visits.
Willie, the Jolly Olly Man (voiced by Dan Castellaneta) – An ice cream man who is most often referred to as the "Jolly Olly Man," Willie is the driver of an ice cream truck that is frequently seen driving around Arnold's town. Throughout the series, he has been depicted as unfriendly, deranged, depressed, and hated by his employer (who happens to be his father). In one episode, he was the umpire at a baseball game Arnold and his friends played against the fifth graders.
Eduardo (voiced by Carlos Alazraqui) – Eduardo is an anthropologist from a fictional Central American Republic of San Lorenzo. He was friends with Arnold's parents, Miles and Stella, and helped them during their expeditions in San Lorenzo. He is the last person to ever talk to Arnold's parents before they disappeared into the dense jungles.
Harvey (voiced by Lou Rawls) –A mail man who delivers mail and seems to occasionally give advice. He dislikes snow.
Morrie and Vic (both voiced by John Mariano) – a duo often involved in criminal schemes. They set up a counterfeit penny operation in "Wheezin' Ed", work at an auto shop in "Grandpa's Packard", and are also seen as Oskar's friends in various episodes such as "Arnold as Cupid" and "Baby Oskar", frequently seen playing Poker with him.
Abner (vocal effects provided by Craig Bartlett) – Arnold's pet pig. He was a gift from the Green-eyed People at Miles and Stella's wedding from a water basket. Phil first thought to cook Abner but Stella decided to keep the pig. Abner was mistaken for a girl by Stella, who wanted to name "her" Abigail.
