Season 4

Harold, Sid, and Stinky all moon Principal Wartz, but Arnold is blamed, even though he was just an innocent bystander.

Helga's sister Olga comes home for spring break and becomes a classroom aid in Helga's class, much to Helga's chagrin.

After Sid works off a debt with loan shark Big Gino, the two become friends, but when Sid is told to give Arnold a swirlie, he has to choose between the two.

Gerald's older brother Jamie O has a sudden burst of kindness when he finds a girlfriend, but Arnold and Gerald soon find out that the girl is just using Jamie O.

After losing Eugene's birthday party invitations, Arnold feels obliged to throw him another party, but it doesn't work out.

Stinky grows a huge pumpkin to enter in a city competition.

After Bob pops his spine, Miriam runs Big Bob's Beepers. She gets in over her head and forgets about her family.

Arnold finds out that Oskar is illiterate and tries to teach him to read.

Helga wants to show Arnold that she can be as sophisticated as Lila is by taking him, Gerald, and Phoebe out to dinner with a coupon she won. She devises a plan to get out of paying when she discovers they're at the wrong restaurant.

Phoebe is promoted to the sixth grade, but realizes that her new so-called "friends" are just using her to do their homework.

A sleep-talking Helga confides into Bob's parrot about her love for Arnold. The next day, the parrot flies into Arnold's window, and it is up to Helga to get it.

Crisis strikes when Gerald's little sister, Timberly, eats a stock of chocolate turtles that he and Arnold are supposed to sell for a local scout organization.

Helga tries to separate Arnold from Lila while at the annual Cheese Fair.

Harold, after discovering his friends think he is obese, decides to go on a weight-loss cruise. When he comes back, though, he is noticeably larger.

After Grandpa tells Arnold that he never got his grade school diploma, Arnold convinces him to come to go back to school at P.S. 118.

Arnold and Helga must care for an egg for a school project about parenting. Meanwhile, Rhonda and Harold are project partners and must also take care of an egg.

Helga becomes a model, but she quits after she gets irritated at everyone dressing like her.

Arnold's classmates are tired of constantly telling them the right thing to do, so he stops giving them advice. Nevertheless, when his classmates get into sticky situations, they are in desperate need of his advice.

After getting in a car accident, Bob and Grandpa face off on the golf green, with the loser having to pay for the damage to both cars.

Rhonda attends a finishing school, but is far from impressive with her stroppy attitude, and seeks help from fellow student Big Patty.

Arnold's bland country cousin, Arnie, comes to visit. Arnold begins to notice that Arnie and Lila show interest in each other, making him jealous.

Oskar has to take care of his infant cousin-in-law (also named Oskar), while both Susie and her cousin are gone.

Phil's twin sister comes for a visit, bringing along an unsettled conflict between them.

Arnold and the gang are part of a synchronized swimming team led by Coach Wittenburg.

After eating pork rinds, Helga sleepwalks, uttering her secret about Arnold as she does so.

Arnold, Grandpa, Grandma, Ernie, and Mr. Hyunh compete on a game show against a "perfect" family from PS 119

Arnold tells an urban legend about a decapitated taxi driver. The gang goes out, only to find the details in the story are becoming real.

Arnold and Gerald try to prove superstitions are fictitious, only for it all to backfire on them.

Arnold's Grandpa recalls his adventures as a soldier in the Second World War, outwitting a regiment of Nazis, while Gerald's dad, Martin, remembers his own time serving in Vietnam.

Helga confides in the school psychiatrist about her social life, family life, and her love for Arnold.

Dino Spumoni is found missing and then declared dead after what appears to be a suicide attempt. but Arnold finds out that this isn't the case, and he secretly lives in the boarding house, believing that his work will skyrocket in value after his "death".