This is a listing of characters from the Nickelodeon animated television series Hey Arnold! and Hey Arnold!: The Movie.
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 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.