A rare sense of humour and irony distinguished the chubby rapper, now 34, from his peers in the manufactured world of K-pop and made him an unlikely worldwide success.
As of Sunday "Gangnam Style" - whose wacky music and dance moves mock the hedonistic lifestyle of the upmarket southern Seoul neighbourhood - had registered almost 814 million views in four months.
The video has inspired thousands of online imitations of Psy's famous horse-ride dance, and flash mobs of tens of thousands in Paris, Rome and Milan.
The song peaked at number two on the US Billboard's pop chart for seven weeks in a row after sweeping the charts in countries including Australia and Britain.
World figures swept up in the fever include UN secretary general Ban Ki-moon, British Prime Minister David Cameron and US President Barack Obama, who either tried out the dance or marvelled at its popularity.
Psy, whose real name is Park Jae-Sang, gained the ultimate showbiz accolade by teaming up with Madonna in the pop diva's concert and performing a special version of "Gangnam Style" with MC Hammer in the American Music Awards.
YouTube called the music video - which Saturday overtook Justin Bieber's "Baby" in number of views - "a massive hit at a global level unlike anything we've ever seen before".
Billboard.com noted it racked up the YouTube milestone in about four months compared to more than two years for "Baby", calling it "nothing short of a pop culture phenomenon".
Psy's dramatic rise has been viewed with a mixture of pride and surprise in his home country, whose music industry has long been dominated by prettified, highly-manufactured girl and boy bands.
Having taken Asia by storm over the past decade with bubblegum hooks and dance moves staged with military precision, K-pop in recent years has garnered a small but growing fan base among teenagers in parts of Europe and America.
But none has come close to the worldwide popularity of the homely Psy.
"Psy is right at the opposite of our typical K-pop stars who are extremely preened and whose every single move is strictly dictated by their agent," prominent music critic Kang Hun told AFP.
Humour, especially satire, is rare in the mainstream Korean music scene and that, coupled with Psy's embrace of his anti-pop idol looks, has set him apart.
The singer, well known at home for his humorous and explosive stage performances, has long been a somewhat provocative figure in Korea.
He was once convicted in Seoul of smoking marijuana. Several of his earlier songs and music videos were banned for those aged under 18 because of what state censors deemed to be overly sexual lyrics or bad language.
In 2007 Psy was forced to serve a second period of compulsory military service after it was revealed that he had continued with his showbiz interests during his first two-year stint.
"Psy has long had very freewheeling, humorous and even provocative elements in his songs which are utterly lacking in most young K-pop idols," Kang said.
"I think 'Gangnam Style' is a pinnacle of such a humourous, non-serious bad-boy style of his. And apparently people around the world can relate to his self-deprecating sense of humour."
Psy himself says he invites laughter and not ridicule.
"My motto is to be funny, but not stupid," he once said in an interview with Yonhap news agency.
It remains to be seen if "Gangnam Style" will prove anything more than a one-hit wonder. Psy is set to release a new album in English and Korean early next year which will be distributed globally.
But even if it takes off, it will be hard to replicate the success of "Gangnam Style", said Han Koo-Hyun, the head of the Korean Wave Research Institute.
"His next song will be able to rack up at least hundreds of millions of views due to the popularity of 'Gangnam Style' but will never be more popular than 'Gangnam Style', said Han.
"This is too huge a success to accomplish twice."