Stephen Hillenburg, who created SpongeBob SquarePants and the absurd undersea world he inhabited, has died at age 57, Nickelodeon announced Tuesday.

Hillenburg died Monday of Lou Gehrig's disease, also known as ALS, the cable network said in a statement. He was 57.

Hillenburg had announced he had the disease in March 2017. His death comes just weeks after the passing of another cartoon hero in Marvel creator Stan Lee.

An Oklahoma native with a love of both drawing and marine biology, Hillenburg conceived, wrote, produced and directed the animated series that began in 1999 and went on to spawn hundreds of episodes, movies and a Broadway show.

"He was a beloved friend and long-time creative partner to everyone at Nickelodeon, and our hearts go out to his entire family," Nickelodeon's statement said. "Steve imbued 'SpongeBob SquarePants' with a unique sense of humour and innocence that has brought joy to generations of kids and families everywhere. His utterly original characters and the world of Bikini Bottom will long stand as a reminder of the value of optimism, friendship and the limitless power of imagination."

The absurdly jolly SpongeBob, his starfish sidekick Patrick, and a vast cast of oceanic creatures quickly appealed to college kids and parents as much as it did kids.

Hillenburg is survived by his wife of 20 years Karen Hillenburg, son Clay, mother Nancy Hillenburg, and a brother, Brian Kelly Hillenburg. (Andrew Dalton, AP)