Oldham Athletic’s on-loan Burnley striker Michael Mellon fired his dad Micky’s team into the second round with a hat-trick against Northampton Town at Boundary Park.
Mellon scored twice in the first six minutes, including a spectacular overhead kick, against a Cobblers side 26 places above them in the league standings, and added another before Cameron McGeehan netted a consolation.
League One high-fliers Stevenage were also brought down to earth as Lee Bonis tucked away a penalty for Chesterfield, lying seventh in League Two.
Another third-tier side with eyes on promotion also came a cropper as Lincoln City were beaten on penalties by Salford City.
Kelly N’mai scored an equaliser in added time for Salford, with keeper Mark Howard then saving from Conor McGrandles to set up the shootout victory.
The Steve Cotterill-led revival at Cheltenham Town continues with Isaac Hutchinson’s early header guiding the League Two club past League One automatic promotion contenders Bradford.
Since returning to the club in late September, the Robins have lost just once across seven games in all competitions.
Swindon Town were one of five all-EFL upsets by winning 2-1 away at Rotherham United after extra time, despite having Aaron Drinan sent off for throwing a punch at Dan Gore.
Darren Oldaker settled the tie late in the extra period.