West Ham cruise to next round
Brighton edged past Blackpool and Sheffield United beat Plymouth as the other Premier League teams in action avoided embarrassment against lower-league opposition.
Pablo Fornals gave impressive West Ham an early lead at home to Doncaster as they dominated the League One side from the kick-off.
The home side doubled their advantage later in the first half when Andriy Yarmolenko pounced.
An own goal early in the second half from Andy Butler made it 3-0 and Oladapo Afolayan completed the rout.
West Ham, seventh in the Premier League after three straight wins, will play either Manchester United or Liverpool in the next round.
But Brighton did not have it all their own way against League One team Blackpool.
They went 1-0 ahead in the 27th minute courtesy of a thunderous strike from Yves Bissouma but were pegged back in first-half stoppage time by a Gary Madine goal.
The home side restored their lead in the 58th minute when Alexis Mac Allister's shot from distance took a significant deflection off Steven Alzate and beat Blackpool keeper Chris Maxwell.
Goals from Chris Basham and Billy Sharp were enough for Premier League strugglers Sheffield United to see off League One opponents Plymouth.
Elsewhere, Swansea thumped fellow Championship side Nottingham Forest 5-1, while Bristol City beat Millwall 3-0.
Barnsley beat Championship leaders Norwich 1-0.