While Erik Ten Hag's side set aside a difficult start to the season and cruised comfortably through at Old Trafford, Premier League Wolverhampton Wanderers and Luton Town were knocked out by lower-division opponents.
Wolves went 2-0 up and then lost 3-2 at Championship (second tier) high-flyers Ipswich Town while Premier League newcomers Luton were beaten 1-0 at League One (third tier) side Exeter City.
Vincent Kompany's Burnley, without a win in the Premier League so far this season, overran League Two (fourth tier) opponents Salford City 4-0 with a second-string team.
The match was the night's only fixture pitting two top flight clubs against each other and they will meet again in the league at Old Trafford on Saturday.
The draw for the fourth round will be after Wednesday's matches, with 12 Premier League clubs in action and last year's losing finalists Newcastle United hosting Premier League champions Manchester City.
Persons:
Alejandro Garnacho, Crystal Palace's Nathaniel Clyne, Jason Cairnduff, Casemiro, Erik Ten, Demetri Mitchell, Vincent Kompany's Burnley, Dean Henderson, Sam Johnstone, Diogo Dalot, Mason, Anthony Martial, Johnstone, Sofyan Amrabat, Jack Taylor, Freddie Ladapo, Omari Hutchinson, Hwang Hee, Chan, Toti Gomes, Alan Baldwin, Toby Davis, Pritha
Organizations:
Soccer, Manchester United, Companies Manchester United, Crystal, Old Trafford Wolves, Exeter, Luton, Burnley, Salford, League Cup, Crystal Palace, Premier League Wolverhampton Wanderers, Luton Town, Wolves, Ipswich Town, Premier League, League, Exeter City, Salford City, United, Old, Morocco, Fiorentina, Sky Sports, Ipswich, Middlesbrough, Bradford City, Mansfield Town, League One Peterborough, Sutton United, Port, Newcastle United, Manchester City, Thomson
Locations:
Old Trafford, Manchester, Britain, Old, Ipswich, Salford MANCHESTER, England, Exeter, Saturday, Port Vale, London