The oldest millennials are in their 30s, but already they're starting to feel nostalgic for their youth. That's why Nickelodeon is bringing back 'Hey Arnold! The Jungle Movie' 13 years after the animated show ended.

Craig Bartlett is the creator of 'Hey Arnold.' "He's this calm center around in which everything happens," Bartlett says, explaining his initial pitch to the studio."He always tries to help people, whether they deserved it or not." 

Bartlett says there were campaigns on Facebook with tens of thousands of signatures asking Nickelodeon to save the show, which ended on a cliffhanger back in 2004. With so much demand building online, Nickelodeon decided to bring 'Hey Arnold!' back. There's a new actor playing Arnold, but fans will hear some familiar voices too.  

Francesca Marie Smith and Craig Barlett sitting on the stoop at Nickelodeon, Burbank

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Jody Au Yeung

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Francesca Marie Smith was nine years old when she first played the part of Helga Pataki. She's the girl who seems to hate Arnold but is secretly in love with him. 

Being a voice actor as a child inspired Smith to pursue a PhD in media theory at USC's Annenberg School.  "The Jungle Movie' obviously was a direct response to and very much integrated into the fan community and the fan response," Smith says.

Justin Shenkarow, the voice of Herald Bergman, returns to Hey Arnold, the Jungle Movie

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Justin Shenkarow

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Justin Shenkarow also returns from the original. He plays Herald Bergman, a bully with a soft side. "In real life, I'm the opposite of a nerd. I was teased growing up for having a big fro, so I really channeled that energy into portraying a vulnerable, almost lovable bully," Shenkarow says. 

Now Shenkarow is an established actor, with credits on franchise films like 'Avatar' and 'Ice Age.' He's also put a positive spin on his hair by naming his production company "Shake That Fro."

Even he feels nostalgic toward 'Hey Arnold!' "I think millennials really long for that incredible time period in their life. With all the instability in the world, economically and politically, it's a bit scary," Shenkarow says. "Hey Arnold!' really represents their youth, just the fact that we were in a much happier world at that point." 

Fan art from all around the world for Hey Arnold after the series had ended.

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Jody Au Yeung

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There's a lot at stake for fans, and some wonder if the new movie will live up to their old memories.

'Hey Arnold! The Jungle Movie' premieres Friday, Nov. 24, from 7:00-9:00 p.m. (ET/PT) and is available for download on Saturday, Nov. 25.