The football world sat up in wonder last night. Barcelona reigned supreme as Neymar, Lionel Messi and Luis Suarez produced 45 minutes of football that may never be forgotten.
At times, the magical trio defied the laws of physics. At others, they defied the laws of football - like that one that usually sees you score a penalty with one touch...
But Celtic fans sat up for a different reason. Indeed, as thrilled as they would have been by Barcelona (who wasn't?), it was Celta Vigo's scorer that was most intriguing for the Celtic faithful.
Celta lost 6-1 but were briefly level at 1-1, after John Guidetti scored a penalty of his own.
And it got Bhoys fans talking. Many couldn't believe the fact Celtic let the striker go only for him to be netting against the great Barca just a few months down the line. Others cited the fact he could have been brought to Parkhead on a permanent basis, only for Celtic to go for Nadir Ciftci instead.
There were plenty, though, who felt Guidetti didn't have the mentality to succeed in Glasgow - as well as the fact he made it clear he wanted to leave in the end.
Here's how Celtic fans reacted on Twitter to his performance v Barcelona...
Why is Guidetti's name coming up tonight? Guy chucked it after Inter Milan last year, doesn't have mentality to succeed at Celtic— Paul (@pauln1984) February 14, 2016
That Guidetti lad scoring v Barca tonight can't possibly be the same lad Celtic had last season...— Conor Leeson (@conorleeson) February 14, 2016
#guidetti has scored at the Camp Nou and I want to choke myself with my Celtic scarf because what is life?— TomTomski (@TommyTomski) February 14, 2016
There's John Guidetti, the man Celtic fans chased out of the club, scoring against Barcelona— Waldo (@OdLedge) February 14, 2016
John Guidetti scores at the Nou camp. Still not good enough for Celtic though...— Bradley Abbott (@bradleyabbott_) February 14, 2016
There's not a day that goes by when I don't miss seeing John Guidetti playing for Celtic— Jenky (@Jenky67) February 14, 2016