It has been established for a while that Nickelodeon is working on a full-length film reboot of its popular 90s cartoon, Hey Arnold! The first screens and the character designs were only just revealed, though, reports E! News, and they are quite stirring for anyone who was familiar with Hey Arnold! when it graced the small screen.

Nickelodeon unveiled the new images for the film, entitled Hey Arnold!: The Jungle Movie, at its recent Comic-Con 2016 panel.

A screen shot from the film revealed at Comic-Con. Gerald, left, and Arnold are sitting on the front stoop of their boarding house while Helga stands aside, scowling. [Image via Nickelodeon]Fans of the Hey Arnold! TV show, which aired from 1996 to 2004, will recognize the three main characters -- Arnold, Gerald, and Helga -- in the sole screen shot revealed from the movie. All three of their designs look pretty true to their depictions on the show, a fact that E! points out sets this new Hey Arnold! filmic endeavor apart from other reboots of old classics; in most other revivals, the source says, the central designs of the setting or characters are tweaked to reflect a more modern vibe.

Hey Arnold! fans might also recognize Sunset Arms, the boarding house that houses both Arnold and Gerald and which the two are sitting in front of in the screen shot. Like the characters themselves, almost everything about the old red brick boarding house looks comfortably familiar.

The only obvious indicator that the screen shot is not just taken from an episode of the Hey Arnold! TV series: the polished, glossy sheen provided by much more modern animation software.

The other images released at Comic-Con are not screen shots, but show off tooled-up designs for some of the more important Hey Arnold! characters, including Arnold's energetic Grandpa and the family's trusty pet pig, Abner, as well as Pheobe, Helga's bookish best friend. The main three characters are expanded upon, too.

The character designs are great at reflecting the character qualities viewers grew to know and love during Hey Arnold!'s original run, from Arnold's football-shaped head to Gerald's awesome basketball skills to Pheobe's endearingly whimsical nature to the scowl that so frequently finds its way onto Helga's face.

A lineup of several characters, including Arnold's grandpa, left, and Abner the pig, right. [Image via Nickelodeon] Helga's character sketch. [Image via Nickelodeon] Gerald's character sketch. [Image via Nickelodeon] Arnold's character sketch. [Image via Nickelodeon] Phoebe's character sketch. [Image via Nickelodeon]The question now is, what will the plot of Hey Arnold!: The Jungle Movie be? Even though the movie was announced by Variety back in November of last year, Nickelodeon has kept mum when it comes to revealing any details. All that is known is that the movie will answer the question of the identities and whereabouts of Arnold's parents, one of the largest unsolved mysteries of the Hey Arnold! universe.

No matter what the plot, though, it is highly likely Hey Arnold!: The Jungle Movie will retain the indefinable charm of the original series, because, as fans will be happy to hear, series creator Craig Bartlett will be writing and executive producing the films.

Another element the film is retaining from the original shows and that will undoubtedly make Hey Arnold! purists very happy is most of the voice acting. Unfortunately, the two most central characters, Arnold and Gerald, will be voiced by newbies, since the now-adult actors who voiced them before can no longer produce the children's voices they could before. Other than that, though, pretty much all the big characters -- from Phoebe to Helga to her older sister Olga -- will be voiced by the same people as in the show.

Hey Arnold! is not the only retro series that Nickelodeon is electing to bring back as a movie, The Inquisitr reported. Other 90s favorites like Ren and Stimpy and Legends of the Hidden Temple have also been confirmed to have film adaptations on the way.

Nickelodeon's decision to resurrect Hey Arnold! and other nostalgia-packed 90s gems for a modern audience will undoubtedly prove a very profitable move, as the recent raging success of Pokemon GO shows us that 90s kids and millennials love them some nostalgia -- and are willing to open their wallets for it.

[Photo by Matt Cowan/Getty Images]