Emotional Frank Lampard rescued a point for champions Manchester City against former club Chelsea on Sunday while Manchester United gave up a 3-1 lead to slump to a shock 5-3 defeat at Leicester.
Lampard's equaliser ensured a 1-1 draw against the Premier League leaders who lost their perfect start to the league season but still moved three points clear of second-placed Southampton.
It seemed Jose Mourinho's side were set for a fifth straight league win when Andre Schurrle put them ahead in the 71st minute, shortly after City had been reduced to 10 men by the sending off of defender Pablo Zabaleta.
But former Chelsea great Lampard, only playing for City after being loaned to them by New York City, the club he left for at the end of last season, drew the hosts level five minutes from time following a typically late run into the box.
The drama at Eastlands was as nothing compared to events earlier in the day at Leicester's King Power Stadium.
It seemed big-spenders United were on course for their first competitive away victory under Louis van Gaal after goals by Robin van Persie, Angel di Maria and Ander Herrera left them 3-1 up with just over 30 minutes remaining.
But a controversial penalty, converted by David Nugent, reduced the Foxes' deficit to 3-2 after they had got on the scoresheet through Leonardo Ulloa.
Two minutes after Nugent's penalty, Esteban Cambiasso drew Leicester level at 3-3 before Jamie Vardy, given time and space, made it 4-3 in the 79th minute.
Four minutes later, Ulloa made the game safe for promoted Leicester when, after United's Tyler Blackett had been sent off for bringing down Vardy in the box, the striker scored his second goal and Leicester's fifth from the penalty spot.
"How is it possible to give this game away?," a disbelieving van Gaal told Sky Sports.
"We have given the game away. Leicester has proven already in four games that they have a strong character and that when they are 3-1 down, you can play all the game with more possession but you cannot do these kind of things."
- Leicester spirit -
Delighted Leicester boss Nigel Pearson said: "To back up the Stoke win against one of the big forces in English football is very satisfying.
"When you add to that coming from 3-1 down, it is a testament to the quality, belief and spirit amongst us."
United, fresh from their 4-0 thrashing of QPR, like Leicester a newly-promoted side, 2-0 up inside 16 minutes.
Van Persie opened the scoring in the 13th minute when the Dutch striker headed in an excellent cross from Radamel Falcao.
Di Maria then showed why United had paid a British record fee of 59.7 million pounds ($98 million, 75 million euros) to Real Madrid with a sublime second goal, courtesy of a perfect chip over Kasper Schmeichel -- son of United goalkeeping great Peter.
But just two minutes later Leicester pulled a goal back through an Argentinian ace of their own when Ulloa powered in a near-post header following an excellent cross by Vardy.
Herrera made it 3-1 before Leicester were given a contentious lifeline in the 62nd minute.
Vardy barged Rafael outside the box but referee Mark Clattenburg let play continue only to point to the penalty spot when, with roles reversed, the Leicester man went down inside the area following a slight touch by the full-back.
Leicester were all square minutes later when Cambiasso became the third Argentinian to score in the match, with a low shot from inside the box.
Then came Ulloa's penalty that set the seal on a memorable win for Leicester.
Meanwhile West Bromwich Albion and Crystal Palace, who had started the day as the top-flight's bottom two clubs, moved up after wins away to Tottenham Hotspur and Everton respectively.
At White Hart Lane, Scotland international James Morrison's 74th-minute header secured a 1-0 victory for West Brom over Spurs.
West Brom's success meant Palace kicked-off bottom of the table at Goodison Park later Sunday, but they responded with a 3-2 win
Palace were behind early on after Romelu Lukaku gave Everton a ninth-minute lead.
But the Eagles soared thanks to Mile Jedinak's 30th-minute penalty and second-half goals from Fraizer Campbell and Yannick Bolassie, with Leighton Baines's 83rd-minute penalty too little, too late for Everton.