League One Bradford served up one of the biggest shocks in FA Cup history as they hit back from two goals down to beat Chelsea 4-2 at Stamford Bridge.
And on an extraordinary day in the world’s oldest knockout competition, Manchester City were also left reeling by a 2-0 defeat at home to Championship Middlesbrough.
Former Boro winger Andy Halliday was the Bantams hero as he fired home from outside the box to give Phil Parkinson’s men a stunning lead with eight minutes left in west London.
And when substitute Mark Yeates fired home deep into seven minutes of injury time, one of the most miraculous results in the history of the competition was complete.
The visitors’ starting line-up cost the princely sum of £7,500 – paid to non-league Guiseley for James Hanson in 2009 – while the total fee for Chelsea’s parade of stars almost reached £200million.
Jose Mourinho’s men had won all 10 of their home Premier League games so far this term – but Bradford were undaunted and signalled their intentions early when Andrew Davies forced a point-blank save out of Petr Cech in the 14th minute.
There was no hint of the excitement to come when Gary Cahill put Chelsea in front on 21 minutes and Ramires made it two with an excellent strike.
But Jon Stead reduced the deficit before half-time and former Chelsea junior Filipe Morais grabbed a surprise equaliser on 75 minutes before the late drama.
Meanwhile in the north-west Aitor Karanka’s Boro were fashioning a result of similar magnitude as goals from Patrick Bamford and Kike sunk Manuel Pellegrini’s stars.
Boro keeper Tomas Meijas kept his side in the game with a series of stunning saves in the first half before Bamford – ironically on loan from Chelsea – put the visitors in front of 53 minutes.
Albert Adomah beat keeper Willy Caballero to a poor Fernando backpass and prodded the ball goalwards for Bamford to slide in with the follow-up.
And Boro completed their own improbable win in injury time when Kike was slipped through by Bamford and shot past Caballero.
Late goals from Leonardo Ulloa and Jeffrey Schlupp saw Leicester hit back from behind to beat Tottenham 2-1 at White Hart Lane.
Spurs looked set to ease home in a low-key encounter after Andros Townsend hit a 19th-minute penalty past 42-year-old Foxes debutant Mark Schwarzer.
But Ulloa steered home a low left-foot equaliser before Dutchman Schlupp stole the show deep into injury time with another left-foot strike.
Marouane Chamakh scored twice to continue Alan Pardew’s winning run as Crystal Palace boss with a 3-2 victory over Southampton at St Mary’s.
All five goals came in a breathless first 39 minutes with Graziano Pelle putting Saints in front on nine minutes before Chamakh equalised two minutes later.
A Scott Dann own goal restored the hosts’ advantage but Yaya Sanogo’s rising effort equalised for the Eagles and Chamakh got his second six minutes before the break.
Two goals from Victor Anichebe helped West Brom survive a tricky test against Midlands rivals Birmingham at St Andrew’s.
The Baggies made the most of a sloppy start from the hosts with Anichebe hitting the opener on 25 minutes and notching his second 10 minutes later.
But the Blues rallied and made a game of it after Jonathan Grounds reduced the deficit with a low shot off the post in first-half injury time.
Sunderland had Jack Rodwell sent off as they battled out a dismal goalless draw against Fulham at the Stadium of Light.
Rodwell had already been booked when he senselessly blocked a throw by Fulham keeper Marcus Bettinelli in the 66th minute, leading to his dismissal.
Darren Bent headed the opener on his full debut as Derby beat neighbours Chesterfield 2-0, Will Hughes completing a hard-earned victory for the Championship side with eight minutes to go.
Substitute Hal Robson-Kanu grabbed a fifth round place for Reading as the Royals came from behind to beat Cardiff 2-1 in south Wales.
Kenwyne Jones’s 25th-minute header put the Bluebirds in front before Oliver Norwood equalised and Robson-Kanu pounced to win it two minutes from time.
Preston and Sheffield United must do it again after a 1-1 draw at Deepdale, Paul Gallagher putting the hosts in front before Diego De Girolamo equalised midway through the second half.