|“||I think your heart... is more pure than you know.||„|
|~ To Helga|
Arnold's head is shaped like an American football, thus earning him the nickname "Football Head". He is usually seen wearing his favorite blue hat and an oversized red plaid button up underneath a teal sweater. In the pilot, his sweater is orange and his undershirt is blue.
Arnold is kind, caring, brave, calm, peaceful, self-less, smart, and wise. Arnold often daydreams and has had a wild imagination, this has been a trait since the character's conception. He is very forgiving and sympathetic towards Helga, despite her constant harassment of him to hide her true feelings. Throughout the series, he is completely unaware of Helga's feelings for him, other than the occasional hint from Helga and other classmates. Arnold also likes listening to Jazz.
Arnold Shortman was born and raised in the fictional city of Hillwood. He lives at the Sunset Arms boarding house with his Grandpa Phil and Grandma Gertie, as well as four other boarders who rent. Arnold's room is located in the attic which has been converted into a bedroom. When Arnold was a baby he was left with his grandparents while his parents went off on a mysterious trip to San Lorenzo; Sadly they never returned. Despite the tragic loss of his parents, Arnold is very strong willed and is always willing to help others that are in need. Arnold also has a pet pig named Abner who he cares for a lot.
In Hey Arnold!: The Movie, a greedy developer named Scheck plans to tear down Arnold's neighborhood and in it's place build a huge "mall-plex". Arnold and Gerald undertake a huge mission to recover an incriminating document and ultimately save the neighborhood.
In Hey Arnold!: The Jungle Movie, Arnold and his best friend Gerald plan to make a humanitarian video during the summer, after their fifth grade year to win a trip to San Lorenzo. This is where Arnold's parents were last seen, as mentioned in the final episode of the series The Journal.
They try to record themselves making a home out of junk for one of their friends, eccentric Monkeyman, but that backfires; Arnold leaves, heartbroken. Arnold returns Helga's feelings with a kiss of his own, after thanking Helga for her help in finding his parents and using her locket to help activate the device that releases the cure to the sleeping sickness which his parents had contracted before they could release the cure. It's also implied at the end of the movie that he and Helga become a couple, as Arnold holds hands with Helga (although Helga pretends to be hostile to Arnold in public).
- According from Hey Arnold's creator, Craig Barlett himself; Arnold and Helga do get married and have children.
- While his surname is never revealed in the show, it was confirmed to be Shortman by Craig Bartlett in an interview with BuzzFeed (and talked about in The Jungle Movie), it was also hinted in the show by his Grandfather.
- Throughout the series' run, he was voiced by at least five different voice actors:
- J.D. Daniels (who did his voice in the pilot)
- Toran Caudell (who was also the voice of the bully Wolfgang)
- Phillip Van Dyke
- Spencer Klein (who did his voice in the movie), and
- Alex D. Linz who did April Fool's Day and The Journal.
- Mason Vale Cotton (who did his voice in the second movie)