Holders Chelsea and Premier League champions Manchester United were bundled out of the FA Cup quarter-finals on Saturday in one of the most dramatic days in the competition's recent history.
Chelsea lost 1-0 at Championship (second division) side Barnsley, who reached the last four for the first time in nearly 100 years thanks to striker Kayode Odejayi's 66th-minute header.
Earlier, Portsmouth won 1-0 at Old Trafford as Ghanaian Sulley Muntari's second-half penalty sealed their first victory at United for 51 years.
After years of domination by England's so-called big four clubs going back to 1996, this year's FA Cup has produced several stunning upsets and the possibility of a team outside the Premier League winning the trophy.
Sunday's quarter-finals feature Premier League strugglers Middlesbrough at home to Championship team Cardiff City and League One (third division) Bristol Rovers at home to Championship high-flyers West Bromwich Albion.
Nigerian journeyman Odejayi, formerly with minor league Forest Green, was the hero for Barnsley on a bumpy Oakwell pitch.
He had already caused Chelsea captain John Terry a host of problems before out leaping keeper Carlo Cudicini to head the only goal.
Chelsea launched a wave of desperate attacks in the final minutes with Terry shooting wildly over and several efforts being blocked. But the hosts hung on to spark wild celebrations.
"I'm ecstatic, I can't believe it," Barnsley manager Simon Davey told the BBC.
"Everybody thought we couldn't do it again after beating Liverpool (at Anfield in the previous round). The players were fantastic. I've never been to Wembley before and nor have many of the players."
Two weeks after losing the League Cup final to Tottenham Hotspur, Chelsea manager Avram Grant is sure to come under fire.
"Credit to Barnsley, they showed a lot of spirit," said Grant. "We knew it wasn't easy to play well on this pitch and we didn't, especially in the first half."
SMASH AND GRAB
Portsmouth produced a classic smash and grab raid to reach the semi-finals, which are being held at Wembley this season, for the first time since 1992.
They were under siege for long periods but a penalty 12 minutes from time by Muntari, after United keeper Tomasz Kuszczak had been sent off for fouling Milan Baros, earned a memorable victory.
"It was the worst draw we could have got but it was a great performance and a great result," Portsmouth manager Harry Redknapp told Sky Sports.
"We rode our luck but United are a fantastic team and we deserved our luck," added Redknapp, who also led Bournemouth to victory over United in the 1984 competition.
Portsmouth had a huge letoff in the first half when Sylvain Distin barged Cristiano Ronaldo as the United winger surged into the penalty area.
Sol Campbell was outstanding at the heart of Pompey's resistance while keeper David James produced one top-class save to turn a Patrice Evra shot against the post.
Michael Carrick also looked certain to score for United only for Distin to make a brilliant last-ditch tackle.
Just when it seemed Portsmouth would crack, they scored.
A quick kick by James picked out Croatian Niko Kranjcar and he squared for the unmarked Baros.
The Czech went round Kuszczak, who came on at halftime for the injured Edwin van der Sar, before being fouled by the Polish keeper who was shown the red card.
England defender Rio Ferdinand took over in United's goal and was powerless to stop Muntari's cool penalty dispatched into the bottom corner.
United manager Alex Ferguson was scathing of referee Martin Atkinson.
"The game was decided by the decision not to give us a penalty," said Ferguson, referring to Distin's lusky escape when he took out Ronaldo.
"They (Pompey) had great confidence to hang on knowing the referee was on their side."