Hillenburg, who graduated college with a degree in natural science and worked at the Orange County Marine Institute, wasn’t a likely candidate for pop culture fame. But he had a longtime love of drawing and incorporated it into his work as a marine biologist. SpongeBob’s characters were born during his time at the Marine Institute, where he created The Intertidal Zone, an educational comic book about tide pools that included a talking sponge, one of many illustrations that would become the characters and scenery in Bikini Bottom.

“I was into Jacques Cousteau as a kid and started scuba-diving around 14, which blew my mind,” Hillenburg told The Guardian in 2016. “It was all colour, another world. I studied natural resources planning and thought I could get a job at some marine park. But I was great at art and so-so at marine biology. It’s funny how the two eventually came together.”

Hillenburg left his job at the Marine Institute to study experimental animation at the California Institute of the Arts. Shortly after receiving his master’s degree in 1992, he joined the staff of Rocko’s Modern Life at Nickelodeon.

Once he pitched the concept for SpongeBob, the first episode aired in 1999. He didn’t expect it to gain a cult following. ''I think we all thought the show would be good, but I didn't ever assume it would catch on in a mass audience sort of way,'' he told The New York Times in 2001. ''That's unexpected, and we're flattered and relieved.''Since then, two SpongeBob movies, a Broadway musical, fashion collaborations with Vans and Moschino, countless consumer products and Emmy nods have helped the talking sponge grow into a global brand. The series has also made its way into meme culture, threading social media with SpongeBob-related jokes.