Maybe it was the beard. Maybe it was those “No Party” t-shirts. Or his passing. Perhaps it was his timeless fashion. That Panenka against England? Did you read the killer autobiography? Or see the video of him leaning on the post?
For me, it was his dazzling EURO 2012, a month-long display of symphonic elegance, so alien to the modern game, that one did not need to analyse or scrutinise, but simply enjoy.
Plenty of Italian footballers perform well late in their careers – think Paolo Maldini, Roberto Baggio, Gianluigi Buffon, Franco Baresi and Alessandro Costacurta – but few completely redefine themselves.
He retired on Tuesday, once and for all, aged 38. But this is not a eulogy to a faded hero who wound down.
It is the story of man whose star, against all odds, shone brightest just before it blew it.
Rarely has a player spent 16 years as a professional and found his best, most meaningful years thereafter. Truly, he was unlike anyone else.
Between his debut in 1995 at Brescia and his final season at AC Milan in 2011, Pirlo enjoyed a fine career, accumulating nine different titles – including two UEFA Champions League victories – and winning approval for his undoubted talents.
He couldn’t get a start at Inter Milan and despite becoming a mainstay with their crosstown rivals after making the move, more seemed to be made about Andriy Shevchenko and Filippo Inzaghi’s goals, Alessandro Nesta’s leadership, Cafu’s runs and Kaka’s weekly world-beating displays.
Eventually Pirlo became revered as a premium, elite passer of the ball, but at the San Siro his name was quickly followed by that of Gennaro Gattuso and Seedorf. It wasn’t until he turned 32 that his talents were truly realised.
What happened next is best summarised by Juventus goalkeeper Buffon, recalling the moment he was told by his chairman, Andrea Agnelli, that Pirlo would be coming to Turin.
"When Andrea told me that he was joining us, the first thing I thought was: 'God exists'. A player of his level and ability, not to mention that he was free, I think it was the signing of the century!"
Contrary to popular opinion, Milan did not release Pirlo: they offered him a one-year deal. He rejected it. He wanted three. Juventus got wind of his demands.
Within a year, The Guardian’s Richard Williams would declare that "no greater misjudgment has been made since Real Madrid sold Claude Makelele to make room for David Beckham."
Makelele became so valuable at Chelsea that his name became a synonym for the role of a holding midfielder whose passing and organisation was so good that he was almost an attacking player.
Ironically, as we sit here today, probably only Pirlo could rival Makelele for effectiveness as a deep-lying playmaker.
When somebody makes a documentary on Pirlo, it will be at Juventus that the triumphant music begins to sound and the slow-motion images take hold.
He only played four seasons in Turin but that brought four league titles. He was in the Serie A Team of the Year every year - which he never managed at Milan - and voted the league’s player of the year in 2012, 2013 and 2014.
Even though his position - on paper – was to screen the defence, in 2011-12 – the year he was meant to be settling in to a new club and a new system – he had more assists than anyone else in the whole league.
And yet for those who didn’t watch Italian football on a regular basis, it will be hard to comprehend how much he single-handedly dominated the league.
Fortunately, when the world tuned in to watch Pirlo play, he rarely disappointed.
He was voted player of the FIFA World Cup final in 2006 but the eternal memory of his international talents will be at EURO 2012.
Written off as a team before the tournament began, manager Cesare Prandelli staked all his chips on Pirlo.
It was a decision with a glorious outcome as Pirlo - unfortunately overlooked for the Golden Ball - brought his full bag of goodies for a glorious month in eastern Europe.
I’m smiling as I recall all this. I’m tipping you’re doing the same – and we’re probably both about to head to YouTube. What a pure exhibition of football. Don't believe me? Ask an Englishman.
The American experiment was a final, well-deserved fling of indulgence, an opportunity to live in Manhattan and smoke cigars in the city that never sleeps.
But now, sadly, the music has stopped and his trademark saying has finally come true: No Pirlo, No Party.