SpongeBob is Nickelodeon’s biggest all-time hit, USA Today reports. The show, which remains popular to this day, originally premiered in May of 1999.

“We are incredibly saddened by the news that Steve Hillenburg has passed away,” Nickelodeon said in a statement. “He was a beloved friend and longtime 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.”

💛 We are sad to share the news of the passing of Stephen Hillenburg, the creator of SpongeBob SquarePants. Today, we are observing a moment of silence to honor his life and work. 💛

— Nickelodeon (@Nickelodeon) November 27, 2018

While SpongeBob made its debut on Nickelodeon, the character also made quite the splash on the big screen and the stage.

In 2015, the character’s first feature film “The SpongeBob Movie” hit theaters. Hillenburg wrote, produced, and directed the film which grossed $140 million worldwide. A second film wrote and executive produced by Hillenburg, “Sponge Out of Water” grossed $325 million worldwide.

SpongeBob SquarePants: The Broadway Musical took home 12 Tony award nominations this year, including a nomination for ‘Best Musical.’ It was also the second-highest grossing Broadway musical, earning more than $19.3 million.

A third SpongeBob movie, “Sponge Bob,” is expected to hit theaters in 2020.