Nickelodeon's <em>SpongeBob SquarePants</em> made its TV debut 25 years ago on May 1, 1999 before the official series launch in July 1999.

Nickelodeon's SpongeBob SquarePants made its TV debut 25 years ago on May 1, 1999 before the official series launch in July 1999. / Nickelodeon

Finish this tune: Who lives in a pineapple under the sea?

If you answered correctly with "SpongeBob SquarePants!" you've likely heard of the square, sponge cartoon who made his TV debut 25 years ago on May 1, 1999 (before the official series launch in July 1999).

But before the "absorbent" and "porous" SpongeBob took over television and movie theater screens, he was actually Bob the Sponge in an educational comic book.

Here's a look at the story behind SpongeBob.

From Bob the Sponge to SpongeBob

SpongeBob SquarePants creator Stephen Hillenburg attended Humboldt University majoring in marine science with a minor in art. After graduating in 1984, Hillenburg eventually began working at the Ocean Institute in Dana Point, Calif. While working as a marine science educator there, Hillenburg illustrated the flora and fauna of tidal pools in the form of an educational comic book called The Intertidal Zone. And the narrator of the comic book may look familiar: a sea sponge with sunglasses and a round face named "Bob the Sponge."

Bob the Sponge, left, in Stephen Hillenburg's original <em>The Intertidal Zone</em> comic book, circa 1989.

Bob the Sponge, left, in Stephen Hillenburg's original The Intertidal Zone comic book, circa 1989. / Stephen Hillenburg/Screenshot by NPR

In 1989, Hillenburg enrolled in the California Institute of Art's Experimental Animation program. After completing the program, he gained more animation experience. Eventually, he was hired as a director on the Nickelodeon cartoon Rocko's Modern Life, which aired from 1993 to 1996. While working on the show, he was encouraged to turn The Intertidal Zone into an animated format, something he could pitch to Nickelodeon.

Speaking to NPR's Morning Edition in 2001, Hillenburg said he worked to develop his characters' design and personalities, including Bob the Sponge.

He described the moment of inspiration: "It wasn't until I drew a square sponge, like a sink sponge, that it really seemed to fit that character that I was looking for, that innocent, squeaky-clean I guess you could say, the square peg in the round hole."

After approving Hillenburg's pitch, Nickelodeon set up SpongeBob SquarePants to be the network's first Saturday morning cartoon.

Fun for all ages leads to a multibillion-dollar franchise

SpongeBob SquarePants first aired as a preview after Nickelodeon's Kids' Choice Awards on May 1, 1999. The first segment of this preview, titled "Help Wanted," is only eight minutes long, yet it introduces a robust coterie of residents in the fictional, underwater town of Bikini Bottom.

From SpongeBob's best friend, a starfish named Patrick (voiced by Bill Fagerbakke); to Mr. Krabs, a greedy, red crab voiced by veteran character actor Clancy Brown; to a grumpy octopus named Squidward (voiced by Roger Bumpass); to two characters voiced by Tom Kenny: Gary, a meowing pet sea snail, and of course, the optimistic and overzealous kitchen sponge and titular character, SpongeBob SquarePants.

"Help Wanted" shows SpongeBob preparing for his dream job as a fry cook at the local greasy eatery owned by Mr. Krabs: "The Krusty Krab."

In promotional art from Nickelodeon, SpongeBob (center) serves

In promotional art from Nickelodeon, SpongeBob (center) serves "Krabby Patties" to patrons: from left, Sandy Cheeks, Squidward, Mr. Krabs and Patrick. / Nickelodeon

Tom Kenny, who worked with Hillenburg on Rocko's Modern Life, took a unique approach to developing the voice for SpongeBob. Speaking with Fresh Air's Terry Gross in 2004 about the process, Kenny said:

"When it came time to come up with a voice, it was just a matter of finding a voice that was childlike and maybe childish, but not a child, non-age specific, enthusiastic and just kind of weird. And we finally settled on this elfish helium voice that SpongeBob wound up being."

The first episode preview contained two more segments: "Reef Blowers" and "Tea At The Treedome"; the latter of which introduced a scientific squirrel who lives in a biodome named Sandy Cheeks, voiced by Carolyn Lawrence.

The series officially debuted on July 17, 1999. That same year, SpongeBob SquarePants beat out the popular Saturday morning cartoon Pokémon in average viewership ratings.

The Cast of <em>Nickelodeon's SpongeBob SquarePants: The Broadway Musical</em> poses onstage during opening night on Dec. 4, 2017, at the Palace Theatre in New York City.

The Cast of Nickelodeon's SpongeBob SquarePants: The Broadway Musical poses onstage during opening night on Dec. 4, 2017, at the Palace Theatre in New York City. / Jenny Anderson/Getty Images for Nickelodeon

SpongeBob SquarePants only grew in popularity. By 2002, the show had almost 56 million total viewers, with almost a third aged 18 to 49, the St. Petersburg Times reported that year. In 2004, its first theatrical release, The SpongeBob SquarePants Movie, grossed $141 million worldwide.

Hillenburg left as showrunner after the movie was released but remained credited as an executive producer on the series and co-wrote the story for 2015's The SpongeBob Movie: Sponge Out of Water.

The Emmy award-winning series is in the midst of its 14th season. And the franchise has expanded to include another theatrical release in 2020, two spinoff television series, more than two dozen video games and even theme park rides.

A musical based on the underwater sponge and his friends took to Broadway in 2017 and had over 300 performances before closing in 2018. The New York Times reported the franchise had generated $13 billion in retail merchandise sales by 2017.

The staying power of SpongeBob

In 2017, Hillenburg announced that he had been diagnosed with ALS, a progressive neurodegenerative disease. He died a year later. As a tribute to Hillenburg, more than one million fans signed a petition for the show's characters to perform at the 2019 Super Bowl halftime show.

Colleagues close to him credit much of the cartoon's success to Hillenburg. Speaking with Fresh Air in 2004, Kenny said Hillenburg balanced attention to detail with the flexibility of the characters.

From left, actor Bill Fagerbakke, <em>SpongeBob SquarePants</em> creator Stephen Hillenburg and actor Tom Kenny attend the premiere of <em>The SpongeBob SquarePants Movie</em> on Nov. 17, 2004, in New York City.

From left, actor Bill Fagerbakke, SpongeBob SquarePants creator Stephen Hillenburg and actor Tom Kenny attend the premiere of The SpongeBob SquarePants Movie on Nov. 17, 2004, in New York City. / Peter Kramer/Getty Images

"Steve Hillenburg definitely is the big kahuna and, a lot of times, just has every vocal nuance and eye blink and twitch mapped out to the nanosecond in his mind," he said. "And then other times, he'll just take you off the leash and go, 'You know, I don't know where this is going. Just take it where it feels funny.' So you never know whether you're going to be doing math or jazz. It's kind of cool."

Twenty-five years after its TV debut, the show continues. SpongeBob SquarePants was renewed for its 15th season last fall and another movie (this one featuring Sandy Cheeks) is planned.

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