By the time the confetti cannons burst, the toddlers were shouting in ecstasy, their eyes fixed on the superstars onstage. Ten costumed performers were delivering the climax of “Baby Shark Live!” — a 75-minute adaptation of a two-minute music video, and an edge case in translating viral popularity into an enduringly profitable real-world franchise.

The global premiere took place on a Thursday night in October at South Carolina’s Spartanburg Memorial Auditorium, and the crowd was split between very young children and their adult caregivers. Siauna Yeargin of nearby Greenville was there with her daughter, Mireya . “When I wash her hair, she wants me to sing ‘Baby Shark,’” Ms. Yeargin said. “I had her first birthday party — ‘Baby Shark.’ Second birthday party — ‘Baby Shark.’”

Four years after the song’s release, by a South Korean media company called SmartStudy, the “Baby Shark” conquest of the planet may well have seemed complete. With just 18 words of lyrics, the song — a zippy story of a shark family out on a hunt — has been streamed on YouTube 3.9 billion times. During the World Series, entire baseball stadiums acted out the video’s shark-bite hand jive. In Dubai, water fountains dance to its beat. Its title alone has become shorthand for an earworm propelled through social media to become 21st-century digital folk culture.

Yet SmartStudy seemed unprepared at first to exploit its hit meme — and is still trying to build a business around it, with the goal of transforming its smiling ocean predator into a children’s brand on the scale of Elmo. To get Baby Shark into every shopping aisle it can, the company has struck licensing deals with Kellogg’s (for limited-edition boxes of “Berry-Fin-Tastic” cereal) and the makers of bedsheets, bath toys, coloring books, clothing, finger puppets and Halloween costumes. A Nickelodeon TV show and a feature film are also in the works.