The club has just released a DVD of 125 iconic moments from its history. Any chance of a product recall and a re-edit? For once Barcelona's exquisite control and movement of a football wasn't enough. Their through-the-eye-of-a-needle play clocked up 76% possession, par for the course, but that statistic didn't count the two times they had to lift it out of their net.
Celtic delivered a display of defending which frustrated and suffocated one of the greatest attacking teams of them all. This wasn't just a backs-to-the-wall, hanging on for dear life job, though. Manager Neil Lennon was the bold architect of the greatest result of his managerial career.
Victor Wanyama's opening goal came from Lennon's training ground and the second was buried by a player who the manager had been brave enough to put on when others would have been defensive. Celtic were 1-0 up when Mikael Lustig went off injured. Lennon shuffled his pack and hauled another striker off the bench. Tony Watt had the night of his life. He scored one terrific goal and could have had a penalty when he got behind Barcelona again. He took them on like he faced them every week.
Celtic beat Barcelona in the 2004 Uefa Cup here but this was bigger. Parkhead has rarely registered a higher decibel count. They were up for this one all right. The noise was thunderous when the players came out at kick-off. At the goals and full-time the foundations shook.
There is always a temptation to suspect that this sort of theatre makes little real impression on players as good as Barcelona's, and that they're mentally yawning at the fuss made over them by yet another set of fans. But there was no denying the astonishing force of the support pouring down on Celtic. Parkhead throbbed.
Celtic knew what they would get from Barcelona but, far more importantly, they also knew what they could get at. Barcelona's claim to be the greatest side of all time always will be questionable because of one fundamental flaw: they cannot defend crosses into their penalty area.
Admittedly their way to cope with that – monopolising possession so that the opposition never get the chance to come at them – is fantastically impressive.
Even so, a team with pace and physical strength inevitably win free-kicks and corners against them. Celtic did so in Camp Nou and they did it again here: and it yielded goals in both games.
Even the times were similar, Celtic went ahead in the 17th minute in Barcelona and the 21st in Glasgow. Over there it was Charlie Mulgrew's free-kick headed in by Georgios Samaras off Javier Mascherano. Here Celtic's goal was even cleaner, even more expertly done.
Mulgrew's corner arrowed over most of the bodies to the back post as Wanyama raced in to bullet a header into the net. Poor wee Jordi Alba, hopelessly ill-equipped to do anything about any of it, was the Barcelona man cowering under the formidable Wanyama.
Barcelona reacted as they had reacted on the six previous times this season when the other team scored the first goal. They camped themselves in Celtic's half, working the ball this way and that, back and fore, probing, probing, probing.
Jordi Alba can't be expected to deal with Wanyama in the air but little else is beyond him. It feels absurd to call him a left-back – for one thing he barely plays in his own half – but his speed, technique and drive gave Barcelona options down the wing as Celtic tried to suffocate them in the middle. Dani Alves was the same on the right. Andres Iniesta, Xavi and Lionel Messi were intricate, brilliant and patient, but just couldn't find a way through.
Kris Commons, Wanyama, Joe Ledley and Charlie Mulgrew presented one wall and the back four was another. Miku dropped back to make it 10, with only Samaras kept upfield to prevent the two Barcelona central defenders from joining all their mates in attack.
All the more admirably, Celtic took it to Barcelona without two of their most important players. Scott Brown succumbed to a sickness bug and Gary Hooper was unavailable because of a hamstring injury. Even Samaras made it only after a late fitness test.
A handful of scares were inevitable. Messi scooped a shot over, then another which kissed the top of the crossbar. Alexis claimed a penalty when Lustig took him down. Towards the end of the first half they cranked it up again. Jordi Alba's ball across the goalmouth had no takers. They hit the woodwork for a second time when Alexis Sanchez's header struck the outside of the post.
Celtic had another chance when Adam Matthews, unusually used at left-back, stabbed a ball across the box which Victor Valdes dived on just before it reached Samaras.
Mulgrew was almost in when a long ball from Efe Ambrose caught Barcelona sleeping.
How Alex Song stayed on the park was a mystery. He was booked for an early foul and committed two more, the second should have been a certain yellow for going through the back of Miku.
When Forster saved from Messi, and then again from Alexis Sanchez, the fans chanted his name. When he flung out an arm to stop a ferocious Messi shot they were almost lost for words.
So much about Barcelona is glorious, but their kingdom is on a weak foundation. They have a defence which cannot be trusted. With seven minutes left, Celtic came at them again. Forster hit it long, Xavi failed to deal with it and suddenly Watt was through. The boy has pace, strength, and finishing which is utterly nerveless. He thrashed it past Valdes and sent the place into pandemonium.
Barcelona had Messi, Xavi, Iniesta, David Villa . . . but they didn't have time. Another matrix of passes resulted in Forster saving from Pedro but Messi burying the rebound in stoppage time. Parkhead held its breath, would Barcelona score at the death again? Not this time. Moments later a whistle sounded and the place exploded.
They had done it: iconic moment No.126.