Western Animation / Hey Arnold!

Hey Arnold! (1996-2004) is a children's animated TV series created by Matt Groening's brother-in-law, Craig Bartlett, starring an eclectic — and more often than not eccentric — group of characters that navigate a sort of urban wonderland. It is the 6th cartoon in the Nicktoons series.

Arnold is a generally mellow 4th-grader with a head shaped like an American football, who lives with his paternal grandparents and their (also eccentric) tenants in a boarding house in Hillwood, Washington. Gerald is his best friend and "the Keeper of Urban Lore," who dispenses legendary tales of characters such as "Stoop Kid" (said to have been born on the stoop he can be seen, day or night, to glower from with promised vengeance to any who should think to violate his sacred site) or "Wheezin' Ed" (rumored to have a massive treasure cavern on the mysterious Elk Island).

Also notable among Arnold's neighbors and classmates is Helga Pataki, a female bully who openly scoffs at Arnold's positive attitude while secretly having a massive crush on him. As the show developed, an increasing amount of focus was put on her extremely conflicted, melodramatic character and her utter obsession with the football-headed one - including her shrines dedicated to him.

The show had a number of episodes dealing with the rather mundane aspects of childhood life, such as the crush on teacher episode, but also ventured into the surreal, such as Arnold and Gerald encountering the labyrinthine realm of the Sewer King to retrieve Arnold's grandfather's watch, and having to duel with him to avoid being declared his "royal rat groomers." In later seasons more attention was paid to the Love Triangle between Helga, Arnold, and Lila, the sickeningly sweet country girl who likes Arnold but does not like-him like him (much to Arnold's chagrin), Helga's transparently dysfunctional and unhappy family life, and the mystery of Arnold's missing parents.

It premiered in 1996, and wound up production in 2001 (though the last episode wouldn't be seen until 2004). It had a theatrical movie in 2002 titled Hey Arnold!: The Movie, originally intended as a TV movie called "Arnold Saves the Neighborhood". Unfortunately, the film didn't fare too well in the box office or the critics. This led to the cancellation of the show's planned second film, "The Jungle Movie". And there... we have trouble. The second movie was the impending Grand Finale of the show, intended to give closure on the fate of Arnold's parents and his feelings towards Helga. For over a decade after the show's cancellation, fans continued to do all they could to bring The Jungle Movie to fruition...

...and their efforts eventually paid off, with a two-part film in the works.

Has an excellent Wiki here, as well as a Best Episode Crowner.

Alternative Title(s): Hey Arnold