Doing the huddle is what Manchester City and fans in England would call the Poznan. It was some sight as 55,000 people turned their backs on one of the most remarkable games the famous old ground has seen, to jump up and down, locked arm to shoulder with people either side of them.
What was revealing was the reaction of the media from Barcelona. The Nou Camp is a football ground where thousands flock daily just to walk around it.
Yet when the huddle started (including the corporate supporters in their suits) several of those from Spanish newspapers stood up and immediately clicked their mobile phones to record. They did the same when home fans blasted out Depeche Mode's I Just Can't Get Enough. As one comment on a YouTube video rightly says, Celtic now own that song.
The Green Brigade, a group of Bhoys ultras who sit in a corner of the ground and often lead the chanting, had worked hard to produce a breathtaking montage before kick-off that spelled out 125 years in memory of the club's foundation in 1887, along with a huge Celtic badge.
It all cranked up the atmosphere to fever pitch. When Victor Wanyama headed in the opening goal after 21 minutes, the ground rocked. When Tony Watt burst through and shot for glory, a crescendo erupted.
The backing was continuous. Depeche Mode, The Fields of Athenry, even Zombie Nation's dance hit Kernkraft 400 boomed around Celtic Park. Neil Lennon had wanted to "bring the thunder back". He got it.
"No words to describe the atmosphere at Celtic Park," Pique typed into his phone as he left the stadium.
Then La Marca gave the man of the match award to Celtic's supporters. "There is probably no bigger home advantage in all of football than at Celtic Park," it wrote.
Praise does not come much higher than that.