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 scored 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 Pounds 7,500 - paid to non-league Guiseley for James Hanson in 2009 - while the total fee for Chelsea's parade of stars almost reached Pounds 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 leftfoot 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.
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.
Liverpool avoided an FA Cup upset but face a replay at Bolton after the Championship side battled out a goalless draw at Anfield.
Neil Lennon's men defended resolutely and had their chances, with Dean Moxey spinning a long-range effort inches wide.
The hosts were curiously toothless but still had much the better of the action with Philippe Coutinho and Fabio Borini among those who forced fine saves out of Bolton keeper Adam Bogdan.
Liverpool's last hope was a late penalty appeal when Jay Spearing appeared to push Jordan Henderson in the box, but referee Kevin Friend waved away the appeals and the visitors stood firm. Arsenal are one of only two teams from the Premier League top six left in the competition after Tomas Rosicky scored one and set up another as the Gunners held off a second-half rally from Brighton to win 3-2 in one of three ties played yesterday.
Arsenal looked to be cruising to victory at the Amex Stadium after Theo Walcott's opener after 90 seconds and Mesut Ozil's close- range finish put the holders two up at the break.
Brighton, however, twice reduced the advantage to one in the second half as Chris O'Grady and Sam Baldock both found the net either side of Rosicky's superb volley to give the home side hope.
The Seagulls poured forward late on and could have had a penalty when Calum Chambers handled in the box with five minutes to play, but the Gunners were spared and it was the holders who sneaked into the next round.
Substitute Diafra Sakho headed West Ham into the fifth round, breaking the hearts of brave Bristol City with an 81st-minute winner.
It was the striker's first appearance since suffering a back injury against West Brom on New Year's Day and he marked it by rising at the far post to beat Frank Fielding from close range after Andy Carroll had done well to get in a cross from the right.
The outcome was harsh on the League One promotion contenders, who were competitive throughout and gave their Premier League opponents all the trouble they could handle.
Carles Gil helped fire Aston Villa into the next round as they avoided an upset to beat Bournemouth 2-1. The midfielder's first goal for the club on his full debut put the hosts ahead against the battling Cherries, who troubled Villa in the first half.
Andi Weimann's second-half strike - his first goal since November - then proved crucial as Villa extended their lead.
Callum Wilson replied deep into stoppage time but the visitors ran out of time to mount a comeback.
Eddie Howe's Championship leaders did scare Villa, though, with Kieran Richardson clearing off the line from Shaun MacDonald and Eunan O'Kane twice going close.
The win was just the third time Villa had scored more than once this season and eased the pressure on boss Paul Lambert.
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