The first episode of "SpongeBob SquarePants," featuring the cheery yellow sea sponge and his friends who live in the fictional underwater city of Bikini Bottom, aired on television in May 1999.

The series went on to win multiple awards, produced a series of spin-off books, two Hollywood movies and a Broadway musical.

"Steve imbued SpongeBob SquarePants with a unique sense of humor and innocence that has brought joy to generations of kids and families everywhere," the Nickelodeon statement said. "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."

Reuters