The song has now been played 7.04 billion times, overtaking the previous record holder Despacito, the Latin pop smash by singer Luis Fonsi.
Played back-to-back, that would mean Baby Shark has been streamed continuously for 30,187 years.
Pinkfong stands to have made about $5.2m (£4m) from YouTube streams alone.
It took four years for Baby Shark to ascend to the top of YouTube's most-played chart, but the song is actually much older than that.
It is thought to have originated in US summer camps in the 1970s. One theory says it was invented in 1975, as Steven Spielberg's Jaws became an box office smash around the world.
There are a huge number of variations on the basic premise, including one version where a surfer loses an arm to the shark, and another where the protagonist dies.
There are also international versions - including the French Bebe Requin and the German Kleiner Hai (Little Shark), which became a minor hit in Europe in 2007.
But none of them could match the phenomenal success of Pinkfong's interpretation, which was sung by 10-year-old Korean-American singer Hope Segoine and uploaded to YouTube in 2015.
It's addictive "doo doo doo doo doo doo" hook and fishy dance moves became a craze in South Korea, where popular bands like Red Velvet, Girls' Generation and Blackpink started incorporating it into their concerts.
The following June, Pinkfong put out a second video, titled Baby Shark Dance, featuring two cute kids performing the dance routine.
That clip that inspired the hashtag #BabySharkChallenge - with everyone from Indonesian farmworkers to pop stars Cardi B and Josh Groban joining the fun.
The song is catnip for children, whose appetite for repetition has undoubtedly helped it climb the ranks of YouTube's most-watched videos.
"Nursery rhymes have always been sort of slow, very cute, but something that would help your children fall asleep - as opposed to Baby Shark," Pinkfong's marketing director Jamie Oh told the BBC in 2018.
"Pinkfong's Baby Shark is very trendy and it has a very bright beat with fun dance moves. The animation is very vivid. We call it K-Pop for the next generation."
The company is turning the song into a movie and a musical, and aspires to make Baby Shark "another classic for kids music, like Twinkle Twinkle Little Star", Oh added.