Hey Arnold The Movie (2002)

Plot
The film opens with Arnold and Gerald returning from losing a basketball game. Arriving at Arnold's boarding house, they see a commotion and learn that a man named Scheck, the CEO of a company called FutureTech Industries (FTI), has just announced plans to redevelop the entire neighborhood as a luxurious high-rise shopping mall. According to a news broadcast, the city's mayor has already approved the controversial redevelopment plan, meaning that the entire neighborhood (33rd-39th street) is going to be torn down and everyone living there will have to sell their homes to FTI and move away. The neighbors decide to sign a petition asking the mayor to cancel the project, to no avail.

During the night, Helga discovers that her father, Big Bob, is working with FTI to build a new super-sized branch of his beeper store in the proposed mall. Helga points out to her father that their neighbors are going to suffer if he builds his store. Big Bob argues that his store is a good thing, because they will become wealthy. Helga ultimately sides with her father, although she's reluctant to do so, due to her feelings for Arnold.

Arnold hosts a protest rally against FTI. However, their permit is stolen by Scheck's employees, so the protest is subsequently declared illegal. The failure of the rally encourages many of Arnold's neighbors to give up. Grandma Gertie is also jailed for being hostile to the police suppressing the protest rally. She tries escaping from jail, but she is continually thwarted. Two days before demolition, Gerald tells Arnold to stop looking on the bright side and that they can not always win, though Arnold is unwilling to accept it.

As the residents begin packing their belongings, Grandpa Phil tells the story of the "Tomato Incident" (a parody of the Boston Tea Party), a major Revolutionary War battle fought in the city. Phil says that the residents of their neighborhood, angry at the increase in British taxes on tomatoes, began a riot that resulted in the British losing control of the city. Arnold realizes that if he can find proof of the neighborhood's involvement in the battle, the neighborhood can be preserve as a National Landmark, stating the neighborhood cannot be demolish. He and Gerald soon learn that the neighborhood was indeed a historic district, but the legal document ensuring its preservation had been sold to a collector, who turns out to be Scheck himself. When confronted, he denies having the document and kicks Arnold and Gerald out of his office.

As the boys are about to give up hope, Arnold gets a mysterious phone call "Deep Voice" informing him that Scheck is lying and the document is hidden in his office safe, and Nick Vermicelli, Scheck's assistant, has the key. Deep Voice directs them to a woman named Bridget, who will help them sneak the key away from Nick. After Arnold and Gerald manage to steal the key, Big Bob, having read the fine print of his contract, finds that Scheck had swindled him out of ownership of his company in exchange for the right to build a new store. He confronts Nick and the two of them fight, with Nick winning. Nick then finds the key gone and alerts Scheck.

Meanwhile, Phil and the men at the boarding house are trying to develop a backup plan just in case Arnold fails to get the document. Phil concocts to wire the storm drain tunnels beneath their street with dynamite to destroy, preventing FTI's construction equipment.

Arnold and Gerald sneak back into the FTI headquarters and locate the safe, but the document is missing. Scheck appears from behind them with the document in his hand. He reveals that his ancestor, the governor of the British forces, was humiliated by the Tomato Incident, and that for years, Scheck has been planning to avenge his family by tearing down Arnold's neighborhood and putting up a hulking building carrying the Scheck name in its place. He then burns the document to ensure that his plans will proceed without question, before summoning his guards to get rid of them. They manage to run and hide from them, feeling hope is lost, until Deep Voice convinces Arnold to obtain FTI security-camera footage of Scheck burning the document. He is nearly caught, forcing him to hide on the roof.

He is then contacted by Deep Voice, who is revealed to be Helga, using a voice-changing toy and calling him from a pay phone in Scheck's building. Arnold asks Helga why she decided to help him, instead of taking her father's side, she reveals that she has feelings for him before kissing him. Helga and Arnold; who is still in shock from Helga's confession, escape the building and meet Gerald on a city bus. Murray, the driver, is unwilling to speed up until he realizes that his girlfriend Mona also lives in Arnold's neighborhood, and that she will be evicted by FTI. Back in the neighborhood, Phil and the gang are waiting with their explosives for FTI to begin demolishing the neighborhood, but Big Bob discovers their plan. Although he states the gang could do some serious jail time for such a radical plan, he decides to help them out with it.

Despite several near-collisions, the kids and Murray eventually make it back uptown to the neighborhood. Meanwhile, Gertie, having managed to escape from jail, hijacks one of the demolition team's bulldozers and sabotages the rest. Soon, the bulldozer and the bus are set to collide. They appear unharmed. Mayor Dixie arrives to the scene, as well as the police and a news crew. Arnold and Bridget show the image of Scheck burning the document to the mayor on the FTI screen, who then officially restores the neighborhood's status as a historic site.

Scheck arrives, demanding to know why demolition work has not begun, seeing his image on the screen, and is promptly arrested. Meanwhile, Nick attempts to escape, only to be punched in the face by Big Bob for his betrayal. Harold, who was woken up by the collision, sits down on the detonator that ignites Phil's explosives. The explosives beneath the street ignite, but destroys the FTI screen instead. Phil and the boarders run away from the police, as Helga talks to Arnold, denying having ever loved him and saying that it was just "the heat of the moment." Arnold, unconvinced, kindly pretends to accept it. Helga returns home cheerfully as Eugene sings a song about the neighborhood being saved, but Gerald stopped him, telling him "show's over."