Transforming back in a nanosecond, he comes over to be introduced. He makes genial small talk. His wife Justine Wheeler, he says, is British, via South Africa, but has Irish blood and they've been to Dublin a couple of times "to see Bono and Ali [Hewson, Bono's wife]". The eldest of their six children is called Sean. He's aged 13. The other five are Kurt, Blake, Eric, Scarlett and Mick ("like Mick Jagger"). He is, he says, very fond of children. "I love the biological side of life."

Because of the gallery's acoustics and the CNN camera crew noisily setting up nearby, we have to lean in to hear each other. His voice is soft and curiously intimate, promising much, but it's soon apparent that Koons sticks with missionary zeal to one topic: promotion of his work. He sprinkles the conversation - as he does every interview you'll ever read or watch on YouTube - with the names of dead artists from Dali all the way back to prehistory.

He says, for example, that his (made in 1985 when he last worked in bronze), is "a masculine (made circa 25,000 BC)". His porcelain (1988) is like Michelangelo's (1499). Watch his interview with singer Pharrell Williams, and you'll see a naked woman appear halfway through to refill the pair's water glasses; Koons blinks, grins, keeps on talking. Perhaps that's also biological.

It was Sean, then aged three, who triggered the series. "I saw him standing in front of a mirror, seeing his whole body for the first time," his father says, reverentially. "It reminded me of Andy Warhol's - it was a male identity thing." He stands up, briefly mimics the cowboy/gunslinger stance. "And I was at a fair and saw Hulk inflatables and it reminded me of the transformative power of Hulk. But I also saw a parallel with the Asian guardian gods, you know, China. Everything was a bridge between East and West."

That was in 2004. Such sudden inspiration, exactly as the art world was eyeing up Eastern markets, was surely heaven sent. Had he actually been to China? "I'd been to some Asian countries but no, not China. I went to Xian's stone museum two years ago and I had one of the most moving experiences of my life." He produces his mobile phone, scrolls through to find a photo of the museum's Buddhas and arhats, facing each other in two rows.

"So pure, so minimal," he murmurs. "That less is more is so clear. I've tried to capture that in the line-up here." He waves over at his Hulks. One glowers over a floral wheelbarrow ("It incorporates a Chineseness"); one has a line of cuddly toys, uncannily similar to a Hong Kong taxi's dashboard, ranged along its shoulders ("It's about co-dependency"); two are heaving a temple bell between them, the bell reproduced from one in the Art Institute of Chicago.

As it happens, Koon studied at the School of the Art Institute of Chicago, a bright-eyed, eager-faced lad from Pennsylvania, the son of a furniture salesman. Photos from the time suggest he's so spookily unaged that the cliché of the portrait in the attic would apply - except that Koons was never the type to hide his image from public view. After his stainless steel , his porcelain and most of all, his disastrous marriage with the Hungarian/Italian porn star, Ilona "Cicciolina" Staller, many people knew more than they wanted to about his life.

With Staller he created the series, which included such photographic creations as . Koons is fond of comparing this work to Gustave Courbet's , which was painted in 1866. As he helpfully points out, if you look at , one of two paintings in the Hong Kong Gagosian show, you'll spot another Courbet reference in the silver, vulvic outline (although modern viewers are more likely to see the artistic dotty origin of Damien Hirst and to wonder what it's doing there).

In 1992, Staller and he had a son, Ludwig, the subject of a bitter, protracted custody battle. Is that missed childhood the reason he subsequently had six more? For a second, he looks surprised, then he says, "And there was another missed childhood - Shannon". She was his daughter given up for adoption when he was a student in Maryland, almost four decades ago, who came to find him when she was 18, and has made him a three-time grandfather.

Mortality is on his mind, what with the Whitney Museum of American Art in New York holding its recent major retrospective and his upcoming 60th, which he plans to celebrate in India.

"A decade went by and I have to say it didn't go that fast and I'd be happy if every decade was like that." But later, he remarks, of life's obsolescence: "It's what Led Zeppelin says: 'When mountains crumble to the sea …' " (Led Zeppelin changed his life at the age of 14. As he puts it, "I'm able to get secretions and respond". Secretions? "Mental ones. To get the biology going.")

His art is extremely costly to produce and there was a low point in the mid-1990s when he only had two assistants, one of whom was Justine Wheeler. Now he employs about 130. Famously, he never touches a work in progress: it's all physically crafted by other hands. What would he create if he were, say, alone on a desert island? "I'd start to build a raft."

Or perhaps an inflatable. "An inflatable gives security," he explains. "Inside us there's mass and density - brain and tissue - while outside is vacuousness. So there's insecurity. But with an inflatable, all of sudden the inside is empty and that gives us density outside."

So apparently inflatable Hulks made of bronze are a joke? "It's not a joke," says Koons, earnestly. "It's a way to get a person to experience transcendence. It's really a philosophical discourse. People look at my work and say, 'Oh, it's … fluffy.' But I see the dark side, the mystic side."

Allure of everyday aesthetic

Jeffrey Koons was born in Pennsylvania on January 21, 1955 to Henry and Gloria Koons. Of his sister, Karen, he has said, "She was three years older so she could jump higher and count better but my parents saw me drawing one day — and patted me on the back".

He began drawing lessons when he was seven. In his teens, he once visited Salvador Dali at his New York hotel and he has cited the Spanish surrealist, along with Marcel Duchamp, as a major influence.

He became associated with the art of "the readymade" — ordinary objects such as vacuum cleaners — during the 1970s but was obliged to work for a while as a commodities trader on Wall Street to fund his work. (1986) — shiny, simple, steely — and his series, including (1988) — pale porcelain, strangely prescient — brought him fame. But it was his (1990) collaboration with porn star Ilona "Cicciolina" Staller that brought notoriety. He destroyed some of it after their marriage ended.

, a 13-metre topiary sculpture, was shown in Germany in 1992, and in 1997, outside the newly opened Guggenheim Museum in Bilbao. The Basque separatist group ETA tried to plant grenades in the flowerpots, shooting a police officer dead in the process.

Another canine series, (1994-2000) was a bigger success. It was made in five colours; the orange version sold at Christie's in November 2013 for US$58.4 million, the most expensive work by a living artist sold at auction.

In June this year, Jeff Koons: A Retrospective opened at New York's Whitney Museum of American Art. Artnet estimated that the work on display was worth more than half a billion dollars. The exhibition transfers to the Centre Pompidou in Paris on November 26 and then to Bilbao next summer.

The late Australian art critic Robert Hughes famously remarked that Koons "couldn't carve his name on a tree". As argues, he's "the signal artist of today's world ... and if you don't like that, take it up with the world".