There's a reason Nickelodeon has Hey Arnold! running during TeenNick's The 90's Are All That! late night block. It happens to be one of the most successful Nicktoons the network ever produced, lasting 8 years of production (1996-2004), in addition to a feature film that wasn't quite so hot at the box office. To think, though, that it all started with some claymation shorts on Pee Wee's Playhouse a decade earlier........!
Series creator Craig Bartlett was also responsible for the Penny shorts that aired on Playhouse, during which a prototype for the Arnold we know and love appeared as a minor character. Bartlett intended to spin Penny off into her own series, or so it would seem, but Nick suits were more interested in the little blond haired kid with a head shaped like a football. Hey Arnold! bowed in October 1996, and became a nightly staple on Nick, even though there really weren't enough episodes to warrant a steady weekday run, but then, this is Nickelodeon we're dealing with here, where they don't care about quantity of episodes, just the ratings.
The following episode showcases the two sides to one of the show's supporting characters, Helga Pataki (I wonder if Bartlett had a certain NY governor in mind), who on the surface is a bullying tomboy, but secretly is smitten with Arnold, though it may not be a secret too much longer after this episode from 2000, "Summer Love". Daniel Hall uploaded the video, which finds the episode already in progress.
While Nickelodeon made what some think was a mistake in creating a follow-up series for Rugrats, the failure of that project allowed them to think twice before trying it with, say for example, Arnold, Helga, and their friends. The series did spend a year or two on CBS' Saturday schedule, back when they were repurposing Nick reruns.