SEOUL — South Korea's Supreme Court has rejected a US composer's allegation that the producers of the inescapably catchy children's song Baby Shark plagiarized his work, ending a six-year-long legal battle.

The court upheld two lower court verdicts that favoured Pinkfong, the South Korean company behind the tune with the "doo doo doo doo doo doo" refrain that has been streamed billions of times.

Jonathan Wright recorded a version of the tune in 2011 based on a children's folk song. Pinkfong's version was released in 2016.

Wright said he owned the copyright to the interpretation, but Pinkfong argued that its version was an arrangement of the same folk song, which is in the public domain.

The court ruled that Wright's version "had not reached a level of substantial alteration" from the original folk song for it to be considered a separate work, which means it is not protected as a separate piece of work under copyright law.

Pinkfong's Baby Shark went wildly viral after it was released on YouTube, in a clip that included hand gestures for children to dance along with.

It became the most-viewed YouTube video of all time in November 2020, at the height of the pandemic, after raking up seven billion views. Just over a year later, it became the first YouTube video to reach 10 billion views.

Baby Shark is thought to have originated in the US in the 1970s and popularised at summer camps. One theory says it was invented in 1975, as Steven Spielberg's Jaws became an box office smash around the world.

The premise hasn't always been as cheery as Pinkfong's interpretation. In one version, a surfer loses an arm to a shark, and in another, the protaganist dies.

Wright, who goes by the stage name Johnny Only, created his sanitised version in 2011. The YouTube video, titled "Baby Shark Song (non-dismemberment version)", features him and a group of children and teenagers dancing to the song by a pool.

Wright said he initially thought, that since the song was in the public domain, "[Pinkfong] could go right ahead and use it".

The idea of a copyright suit arose when he realised that Pinkfong had threatened legal action when a South Korean political party – the current opposition People Power Party – used Baby Shark in a political campaign.

"The wheels in my head start turning... Doesn't that mean that my version also has copyright protection?" Wright told the Canadian Broadcasting Corporation in 2019.

There are also international adaptations of Baby Shark before Pinkfong's interpretation, including the French Bebe Requin and the German Kleiner Hai (Little Shark), which became a viral hit in Europe in 2007.

But none of these have reached the phenomenal success of Pinkfong's adaptation.

Since then, popular acts from Blackpink to Josh Groban have incorporated their version of the song into their performances; it has been translated into more than 100 languages and even been made into a movie.

"We call it K-Pop for the next generation," Pinkfong's marketing director Jamie Oh told the BBC in 2018. — BBC