The English title race became a three-way fight once more after leaders Chelsea were humbled 4-2 at home by Manchester City on Saturday and Arsenal snatched two late goals at Stoke to triumph 3-1 and move to within three points of the top.
Victory for Chelsea would have sent them four points clear of Manchester United at the top but City gave local rivals United renewed hope with a superb performance.
With 10 games to go, Chelsea remain one point clear of United, while City climbed to fourth place, boosting their hopes of claiming the remaining Champions League spot next season.
Cesc Fabregas scored a penalty in the last minute of normal time and Thomas Vermaelen hit the third as Arsenal snatched all three points at Stoke, but their joy was tempered by a horrible injury to Wales teenager Aaron Ramsey, who appeared to suffer a serious leg injury with Ryan Shawcross.
At Stamford Bridge, Chelsea took the lead late in the first half through Frank Lampard but Carlos Tevez and Craig Bellamy scored two goals apiece to seal a famous win.
The match began in contentious fashion when Wayne Bridge refused to shake the hand of Chelsea captain John Terry, after the scandal revolving their personal lives that prompted Bridge to make himself unavailable for England in this summer's World Cup.
Bellamy said the media made a lot more of the situation than the players did, but also took a verbal swipe at Terry.
Some sections of Chelsea fans booed every touch Bridge made and the home side looked like they were on course for victory when Joe Cole fed Lampard and the England midfielder slipped the ball across Shay Given into the far corner.
But City were level almost before Chelsea could settle again. Terry and Ricardo Carvalho made a hash of things in defence and Tevez turned them inside and out before his miscued shot somehow slipped under Chelsea goalkeeper Hilario.
Hilario was also at fault for the City second goal early in the second half. Bellamy's shot from an acute angle was a good one but the goalkeeper again misjudged his angles.
The match was over on 76 minutes when substitute Julian Belletti got the wrong side of Gareth Barry and bundled over the midfielder in the box, handing City a penalty and resulting in a red card for himself.
Tevez made no mistake with the penalty for his second of the game and after Michael Ballack was sent off for a second booking, Bellamy side-footed home after good work from another substitute Shaun Wright-Phillips.
Lampard pulled one back with his second goal, from the penalty spot, after Barry fouled Nicolas Anelka, but it was too little too late.
City manager Roberto Mancini took Bridge off with 15 minutes to go - sparing him another attempted handshake - and was full of praise for the left back.
"Wayne Bridge has been playing well and this team has a fantastic spirit and for this reason we won this game," Mancini said. "It was a difficult game because Chelsea is a fantastic team and has played for many years in the Champions League."
Chelsea manager Carlo Ancelotti said his side lost balance in the second half.
"(That meant) Manchester City were very able to counter-attack, and did a fantastic counter-attack in the second half," Ancelotti said. "It is the first time we lost balance during the game.
"We have to look forward and maintain control of our confidence and we are top of the (table). It is only one point but it is one point. This is not bad. Today is not a good day for us but we have to maintain trust in our quality."
Arsenal are now just three points behind Chelsea after a last-gasp penalty by Fabregas, after Danny Pugh handled the ball, and a third by Vermaelen.
Pugh had given Stoke the lead on eight minutes but Nicklas Bendtner headed the equalizer just after the half-hour mark.
But on 65 minutes, Arsenal's players were visibly shocked as Ramsey suffered a horrendous injury in a challenge with Shawcross, who was sent off.
For 10 minutes, few players made a single tackle but gradually Arsenal made the extra man pay and Fabregas showed his nerve as he converted from the spot after Pugh's handball and Vermaelen secured the win with the third in injury time.
In-administration Portsmouth ended probably the worst week in the history of the club with a fabulous 2-1 win at Burnley.
Frederic Piquionne put them ahead on 25 minutes and though Martin Paterson equalised a few minutes later, a second-half penalty from Hassan Yebda sealed a vital win for the bottom side.
Portsmouth are still waiting to hear if they will receive the expected nine-point penalty for going into administration, but for now, the win at Burnley lifted them to within five points of safety.
James McFadden's first-half penalty gave Birmingham City a 1-0 win over Wigan and lifted them to eighth, while Bolton scored their first goal in six Premier League games to beat Wolves 1-0 thanks to Zat Knight's goal.