Arnold Phillip Shortman is a character and main protagonist of Hey Arnold!
Arnold is a playable character who was invited to compete in a series of races by the Mystery Rider. After the heroes manage to beat the courses which take place in several of their worlds, they learn that the Rider was none other than Sheldon J. Plankton
Arnold is a playable character recruited by Jimmy Neutron after several Nicktoons have been misplaced into eatch other's worlds. Arnold along with the other Nicktoons have to take pictures of each character using the "Neutrino-Cam 4000", a camera that also functions as a teleporter, which will send them back to their own worlds.As the player progresses, it becomes clear that Invader Zim is the mastermind behind the whole mess, and Jimmy soon realizes that after the player has cleared all the levels. Jimmy then flies off in his rocket to Zim's ship and stops the Irken's scheme. After taking a group photo, Zim works on his NEW plan to take over the world, making the ending sequence say, TO BE CONTINUED...
Arnold was originally inteded to be a playable character but was scrapped. He does, however, appear as a Master Model, meaning he was kidnapped by the Saucer Man toys and scanned to make a template that would be used to create evil toy copies of himself, The original Arnold was returned to his home so he couldn't get in the Professor's way.