Scottish midfielder Gary McDonald's first-half strike gave League One Oldham a famous 1-0 FA Cup third-round triumph against mighty Everton at Goodison Park on Saturday.
The League One side, over 50 places below the Merseysiders, fully deserved their victory after a battling performance.
Everton fielded a much-changed side, and McDonald's 25-yard cracker on the stroke of half-time was enough to beat them.
Michael Mifsud scored twice as Coca-Cola Championship club Coventry booked their place in the fourth round with a memorable 4-1 win over Blackburn at Ewood Park.
The Sky Blues, who dumped Manchester United out of the Carling Cup earlier this season with a 2-0 win at Old Trafford, were in good form against Premier League opposition and never looked in danger of losing the lead given to them through Mifsud's crisp volley after 34 minutes.
They doubled their advantage after 64 minutes when Zurab Khizanishvili was adjudged to have fouled Leon Best in the penalty area and defender Elliott Ward coolly stepped up to fire past Brad Friedel.
Dele Adebola added a third from 18 yards before David Bentley scored a consolation five minutes from time for Mark Hughes' beleaguered side.
Mifsud added a fourth in the dying stages as Iain Dowie's side celebrated a memorable day.
Chris Brandon scored nine minutes from time to secure another cup shock as League One Huddersfield beat Premier League Birmingham 2-1.
Luke Beckett handed the Terriers a dream start as he poked home from close range after just four minutes but Garry O'Connor levelled for Blues 15 minutes later.
Huddersfield never looked out of place against their more illustrious opponents and Brandon slotted home from close range late on to book their place in the next round.
Holders Chelsea were made to work hard for their 1-0 victory over neighbours QPR at Stamford Bridge.
They scored the only goal of the game after 39 minutes in fortuitous circumstances as Claudio Pizarro's shot cannoned off the post before rebounding into the net off the back of Rangers goalkeeper Lee Camp.
In other games :
Manchester United progressed as goals in the last 10 minutes from Cristiano Ronaldo and Wayne Rooney saw off Aston Villa 2-0 in the evening kick-off.
Bolton left out a string of first-team players, including Chelsea target Nicolas Anelka, and were made to pay as David Carney's solitary strike put Sheffield United through.
Dave Nugent's third goal for Portsmouth secured a 1-0 win over Ipswich, who had Liam Trotter dismissed in the first half.
Paul Scharner's first-half header, Paul McShane's own goal and a neat strike from David Cotterill helped Wigan cruise past Sunderland 3-0 at the Stadium of Light.
David Wheater's second-half goal ensured there was no upset at Ashton Gate as Middlesbrough came from behind to see off Bristol City 2-1.
Two replays required :
Stephen Hunt matched Dimitar Berbatov's brace as Reading secured a 2-2 draw with Tottenham, who had Tom Huddlestone dismissed for violent conduct.
Manchester City and West Ham will meet again after a dour goalless draw at Upton Park.