Arnold Phillip Shortman is the title character of the Hey Arnold! 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's not sensible to do so. Arnold often acts as the stable center to those around him, whether he's 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 frenemy 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". In the made-for-TV sequel Hey Arnold!: The Jungle Movie, 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 continues to be hostile to Arnold in public). Arnold is friends with most of his fellow fourth-graders, with his best friend 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.
Main characters (Arnold Shortman | Gerald Johanssen | Helga Pataki) | Supporting characters (Phoebe Heyerdahl | Harold Berman | Stinky Peterson | Sid | Rhonda Wellington Lloyd | Eugene Horowitz) | Lila Sawyer)