In one of the biggest upsets in the recent history of the decorated competition, Ben Watson grabbed the only goal as Wigan - who would go on to suffer relegation from the Premier League - triumphed over big-spending City in May last year.
Watson was not available this time around having suffered a broken leg last month but his spirit was invoked by the Wigan players, who wore shirts bearing his picture and the slogan, 'We can do it! For Ben' in the warm-up and went on to spring another sensational shock.
They were given a helping hand, too, by the much-maligned Martin Demichelis, who was arguably at fault for Wigan's two goals.
Things then went from bad to worse for the defender, whose dreadful positioning aided James Perch's strike.
Demichelis' blushes appeared set to be spared when Samir Nasri pulled one back with 22 minutes remaining, but Wigan held on to book a semi-final clash with Arsenal at Wembley and complete a happy return to Manchester for City legend and Wigan boss Uwe Rosler.
The visitors' patience paid dividends in the 26th minute as Gomez sent Costel Pantilimon the wrong way after Demichelis felled Fortune, having been beaten for pace by the striker.
City's frustration increased thereafter as patient build-up play failed to yield openings of any note.
It almost paid immediate dividends as a Dzeko header struck the inside of the post from Clichy's cross.
Wigan's goal then came under siege, with Emerson Boyce's last-gasp challenge denying Dzeko before Scott Carson kept out Sergio Aguero at full stretch, but Rosler's men held on for another famous win.
