Stephen Hillenburg, the creator of Nickelodeons signature cartoon series SpongeBob SquarePants, died on Monday. He was 57.

The animator and former marine biology instructor created a powerhouse property with the quirky SpongeBob SquarePants the global merchandise sales alone have gone north of $13 billion for a brand that has also yielded two animated feature films with a third due in 2020 nine music albums, a video game and a Tony-winning Broadway musical.

Hillenburg revealed in March 2017 that he was battling the neurodegenerative disease ALS, or Lou Gehrigs disease. His death was announced today in a Nickelodeon statement that framed his singular sensibility, which gave the world a loopy but lovable classic of television animation.