Paul Scholes enjoyed a dramatic return to Manchester United as the Red Devils, who led 3-0 at half-time, held on for a 3-2 victory that eliminates holders Manchester City in the third round of the FA Cup.
Scholes, who has come out of retirement to play for United until the end of the season, entered as a second-half substitute - and was culpable as Sergio Aguero cut the deficit to just one, with City having earlier notched through Alexsandar Kolarov. United's goals, all in the opening period, came courtesy of a Wayne Rooney brace and one from Danny Welbeck.
City captain Vincent Kompany controversially saw red in the first half for a two-footed tackle on Nani, leaping into the challenge but making no contact with the Portuguese winger.
United lined up with Rooney in a deeper role than normal, almost operating level with Ryan Giggs and Michael Carrick in the central midfield area, while Roberto Mancini handed a start to Costel Pantilimon, the favoured goalkeeper for domestic cup encounters.
And Pantilimon, with virtually his first involvement of the match, was picking the ball out of the net after ten minutes. From Antonio Valencia's cross, Rooney - who was linked with an Old Trafford exit over the weekend - nodded home, and proceeded to celebrate by kissing the badge on his shirt.
City's plight worsened two minutes later when Vincent Kompany was sent off for his tackle on Nani. United initially struggled to capitalise on their numerical advantage, yet moved 2-0 ahead on the half hour: Welbeck producing a terrific volley inside the penalty box after Patrice Evra's cross was only half-cleared.
Welbeck made another crucial contribution five minutes before the interval, winning the penalty that Rooney converted at the second time of asking after Pantilimon could only parry his initial effort.
Mancini sent on two defenders at half time, seemingly opting to avoid a hammering in the second half, but City pulled a goal back just two minutes into the second period, as Alexander Kolarov - who had earlier given away the penalty - drilled in from 25 yards.
Scholes entered the fray on the hour and, far from offering a composed presence, he soon committed an error which allowed City to reduce the deficit to just one. He underhit a pass, Adam Johnson nipped in to intercept before crossing to Aguero, who converted after his first attempt was spilled dismally by Anders Lindegaard.
United appeared to have taken the sting out of the game heading into the final ten minutes, monopolising possession just in front of the City box - although City had a fine shout for a penalty spurned when a falling Phil Jones appeared to handle Kolarov's cross in the box.
There was nearly more drama deep into stoppage time as Anders Lindegaard parried Kolarov's free-kick straight back into a dangerous area - but, somehow, United cleared and held on for a victory that helps banish the ghosts of the 6-1 reverse they suffered against City earlier this season.
Chelsea scored three goals after the 85th minute in a 4-0 triumph over Portsmouth at Stamford Bridge. The Blues were listless in the opening period, lacking any fluency or urgency, and were lucky to go into the interval on level terms after Pompey's Aaron Mokoena could only nod over from six yards.
However, Chelsea began the second period with more vigour, and Juan Mata put them ahead on 48 minutes, tapping in after Malouda cut the ball back from the byline - although Portsmouth appealed for handball in the build-up. The opener settled Chelsea, but they still failed to scale the heights until a late brace from Ramires - his goals coming in the 85th and 87th minutes - killed the game off. Both were hammered in from close range, and the second came from Fernando Torres' pass. Frank Lampard completed the rout in the 93rd minute, with Ramires turning provider.
Martin O'Neill's transformation of Sunderland continued as they ran out 2-0 winners against Peterborough at London Road. The Black Cats' fourth win in their last five games came courtesy of second-half strikes from Sebastian Larsson and James McClean.
An 88th-minute winner from Chris O'Grady gave Sheffield Wednesday a 1-0 home win over West Ham, who saw Sam Baldock miss a penalty in the second half.
O'Grady swung the balance in the Owls' favour with a low drive drive from the side of the box that stand-in West Ham goalkeeper Ruud Boffin should have done better with, but it was veteran stopper Nicky Weaver who was the star of the show with a number of saves.