Steffen Wohlfarth netted a winner deep into injury time as Ross County completed an incredile comeback from two goals down.
The German beat Kelvin Wilson and Fraser Forster to a long ball to head into the net as the hosts stunned Celtic and consolidated their status as the league's form team of 2013.
The win looked highly unlikely on 21 minutes after Charlie Mulgrew had scored direct from a corner and Gary Hooper chipped home as goalkeeper Michael Fraser endured a nightmare six minutes.
But County also scored twice in six minutes. A stunning volley from Grant Munro and Sam Morrow's close-range finish got them level before the break.
And they emulated their 2010 Scottish Cup win over the Hoops when German substitute Wohlfarth netted his first County goal.
Elsewhere Dundee were left frustrated as Inverness struck late on through Billy McKay for a share of the spoils in a 1-1 draw at Dens Park.
The home side's new interim manager John Brown was all set to celebrate his second win at the helm thanks to John Baird's excellent first-half opener but Caley Thistle hit back through McKay's 82nd-minute header.
With just nine games now left, the Dark Blues remain 14 points behind second-bottom St Mirren but have showed again they are not about to give up the fight for survival yet.
Saints and Dundee United had to settle for a share of the spoils after a goalless draw in Paisley, in which John Rankin was sent off for the visitors two minutes from time.
The hosts, in their last game before taking on Hearts in the League Cup final, looked the likelier scorers in the first half with efforts from Steven Thompson and Esmael Goncalves, set up by Gary Teale.
United were livelier after the break with their two best chances of breaking the deadlock falling late on to substitute Michael Gardyne.
Aberdeen were held to a goalless draw for the sixth time at Pittodrie this season as Motherwell became the latest team to frustrate the Dons.
The Dons have slipped down the table during a run that had seen them score just three times in their previous eight games, and manager Craig Brown welcomed Scott Vernon back into the team in a bid to address that statistic.
But it was not to be, as the toothless Dons racked up another blank and in the end, they were relieved when Motherwell's appeals for a late penalty, after Zaine Francis-Angol went to ground, were dismissed by referee Kevin Clancy.
Second-half goals from Murray Davidson and Gregory Tade boosted St Johnstone's top-six aspirations as they beat Kilmarnock 2-0.
In front of just 2,425 fans, McDiarmid Park's lowest weekend crowd of the season, the Perth side completed a hat-trick of victories this term over Kilmarnock.
The Ayrshire side rarely showed any threat going forward and their hopes of snatching a share of the spoils relied on Saints frittering away chances.
Davidson scored a 58th-minute opener and the home fans finally relaxed when substitute Tade rose to double their advantage five minutes from the end.