“Cobra Kai” producers Jon Hurwitz and Hayden Schlossberg told CNBC on Thursday they have been “stunned” by the success of their sequel to “The Karate Kid.”

The series, which premiered last week on YouTube Red, picks up 34 years after the original movie ends. It brings back the rivalry between Daniel LaRusso, played by Ralph Macchio, and Johnny Lawrence, played by William Zabka.

YouTube, which is owned by Google, announced Thursday it was renewing the streaming series for a second season.

“It’s been unbelievable,” Hurwitz said on “Power Lunch,” noting that the first episode already has over 20 million views.

Hurwitz, Schlossberg and Josh Heald created the series and wrote and directed most of the first season.

“Cobra Kai” is the most recent example of nostalgic returns of fan favorites. Netflix brought back the “Full House” crew with “Fuller House,” ABC has a “Roseanne” reboot, and NBC brought back its sitcom, “Will & Grace.”

The producers, who were behind the movie franchise “Harold & Kumar,” said they approached the series as fans of the original movie and pay homage to the ’80’s classic.

“It tells a story for today’s audience but there’s definitely some callbacks. So if you are a fan of the original movie, you’ll find those moments throughout the first season,” Schlossberg said.

However, they also have a whole new cast of teenage characters they hope will appeal to the younger generations.

“Thus far the reaction has been amazing,” Hurwitz said. “It’s not just people in our age bracket but teenagers have been really into the show as well.”

The Hollywood Reporter summed up the series in a recent review.

“Everything to do with YouTube Red’s ‘Cobra Kai’ sounds like a bit of a joke,” the review states. However, it says, “The thing you don’t expect is for ‘Cobra Kai’ to be pretty decent and to fill its entire first season with enough homages, twists and reversals to be much more consistently entertaining than it has any right to be.”

The fact that YouTube Red appears to have significantly fewer subscribers than other services doesn’t bother Hurwitz and Schlossberg.

In fact, they said they chose the streaming service because they liked what they heard from executives.

“They totally believed in this project,” Schlossberg said. “The truth is, it was a full season without ever having a script generated yet.”

While neither would comment on just how much YouTube Red paid for the series, Schlossberg admitted, “There’s no question they paid the most.”

YouTube Red doesn’t publicly release its subscription numbers, but a 2016 report said the service had 1.5 million paying subscribers.

Netflix has 125 million subscribers, Amazon Prime has 100 million and Hulu has 20 million.

“We’ve been in this business a long enough time to know that the ability to make your product and get it out to the world is invaluable,” said Hurwitz.

“It was nice to us to be the big fish in sort of a smaller pond. If the smaller pond is Google, it doesn’t hurt,” he added.

YouTube Red and YouTube Originals have released more than 50 original series and plan to release 30 more this year.

The second season of “Cobra Kai” is set to begin production this fall and will debut in 2019.