Eugene is a somewhat socially inept, but optimistic friend of Arnold.
Rhonda Wellington Lloyd
Rhonda is 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.
Dino SpumoniDani SpumoniDante Spumoni
Dino is a famous jazz singer loosely based on Frank Sinatra.
Oskar is a lazy, selfish, insecure con artist that remains unemployed through most of the series until becoming a paperboy. He is disliked by pretty much everybody in the boarding house, especially Ernie Potts.
Mr. ChangMr. HyunhMr. Le
Mr. Hyunh 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.
Jolly Molly ManJolly Polly ManJolly Olly Man
Willie, the Jolly Olly Man
He is 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).
Brainy is a geek and Helga's stalker, who is usually knocked unconscious by Helga without Helga even having to look at him. He seems to be romantically attracted to her.
Big BerthaBig SarahBig Patty
Patricia "Big Patty" Smith
Big Patty is 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 (intended for Lila).
Just Kidding, it's Nadine!
Nadine is 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 favor for Helga.
Miriam is Olga and Helga's inattentive mother. It is implied that Miriam suffers from alcoholism, as she often drinks "smoothies" which contain ingredients found in cocktails, she forgets things, speaks in a slow, tired voice, has had her driver's license revoked, has to do community service frequently, and sleeps a lot (often in inappropriate places).
Abner was a wedding present to Arnold's parents and ultimately became his pet.