Holders Chelsea are safely through to the fourth round of the FA Cup but Premier League Cardiff were victims of a giant-killing act by Gillingham.
Cardiff had plenty of opportunities in the first half against the League One strugglers and Nathaniel Mendez-Laing hit the bar in the second period, but they were sunk by a late goal from Elliott List as the Gills got past the third round for the first time in 15 years.
There were no such worries for Chelsea against Nottingham Forest, despite Cesc Fabregas missing a penalty on potentially his farewell appearance at Stamford Bridge.
Alvaro Morata broke the deadlock early in the second half and doubled the lead on the hour to secure a 2-0 win.
League One Accrington produced an upset as Billy Kee's goal 14 minutes from time was enough to beat Championship strugglers Ipswich 1-0.
Ole Gunnar Solskjaer maintained a 100 per cent start to his reign as interim manager as Manchester United beat Reading 2-0 at Old Trafford.
Juan Mata, one of only two players to keep his place in the starting line-up from the midweek Premier League win at Newcastle, gave his side the lead from the penalty spot after VAR was used to judge he had been fouled in the box by Omar Richards.
Romelu Lukaku, making the most of a starting role, doubled United's lead in first-half stoppage time.
Brighton beat Bournemouth 3-1 in an all Premier League tie to book their place in the fourth round.
Early quickfire goals from Anthony Knockaert and Yves Bissouma gave the visitors a 2-0 lead.
Mark Pugh pulled one back for the home side early in the second half but Florin Andone made sure of Brighton's win with their third goal after 64 minutes.
West Ham beat Birmingham 2-0 but early goalscorer Marko Arnautovic reacted angrily to being substituted after just 20 minutes.
His replacement Andy Carroll added a second in stoppage time to secure victory against their Championship opponents.
Burnley squeezed past Championship high-fliers Barnsley 1-0 thanks to a last-gasp penalty from Chris Wood while Aston Villa's new goalkeeper Lovre Kalinic conceded two minutes into his debut as Swansea won 3-0 at Villa Park.
Northern Ireland striker Josh Magennis bagged a second-half hat-trick as Championship Bolton came from a goal down at half-time to beat League One Walsall 5-2, while top-scorer Neal Maupay's second-half penalty was enough to earn Brentford a 1-0 win over Oxford.
Middlesbrough scored five unanswered second-half goals through Britt Assombalonga (two), George Friend, Lewis Wing and Ashley Fletcher in a 5-0 win over Peterborough at the Riverside, where goalkeeper Dimi Konstantopoulos became the home club's oldest player at the age of 40 years and 38 days.
Ademola Lookman's first goal since December 2017 put Everton on their way to a 2-1 win over League Two Lincoln, Kwesi Appiah's last-gasp strike earned Wimbledon a 1-0 victory at Fleetwood, while Bakary Sako scored his first goal for West Brom as they beat Wigan by the same scoreline.
Peter Crouch came off the bench to rescue a 1-1 draw for Stoke at Shrewsbury with his 18th goal in 45 FA Cup appearances, cancelling out a first-half penalty from Ollie Norburn, while Derby and Southampton must replay after battling out a 2-2 draw.
Sheffield Wednesday and Luton will also face each other again after playing out a goalless draw at Hillsborough.