SpongeBob Squarepants creator Stephen Hillenburg has died of ALS. He was 57.

Stephen Hillenburg, who created the Nickelodeon megahit cartoon TV series SpongeBob SquarePants, died on Monday. He was 57.

The cause of death was Amyotrophic Lateral Scleroris, or ALS, which Hillenburg said in March of 2017 he'd been diagnosed with.

We are incredibly saddened by the news that Steve Hillenburg has passed away following a battle with ALS, Nickelodeon said in a statement.

He was a beloved friend and long-time creative partner to everyone at Nickelodeon, and our hearts go out to his entire family. Steve imbued SpongeBob SquarePants with a unique sense of humor 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.

From Variety:

Hillenburg graduated from Humboldt State University in 1984 with a bachelors degree in Natural Resource Planning and Interpretation, with an emphasis on marine resources. He then became a marine biology teacher at the Orange County Marine Institute (now the Ocean Institute) in Dana Point, California. This interest, combined with his artistic talent and love of the sea and its creatures, led him to write and illustrate stories as teaching tools with characters that would later become the denizens of SpongeBobs home, Bikini Bottom.

He began his animation career in 1987, pursuing a degree in Experimental Animation at the California Institute of Arts in Valencia and earning his Master of Fine Arts in 1992.