James McKeown was the hero as Grimsby Town knocked Macclesfield Town out of the Carabao Cup on penalties to book a dream trip to Chelsea.
After a first half which had been shaded by the visitors, the Mariners dominated the contest after the break.
But despite creating some good chances, Town were unable to break the deadlock in open play and the tie had to be decided from the spot.
Macclesfield had an early advantage after Matt Green's kick was saved but McKeown stopped Fraser Horsfall's penalty to bring the scores level.
And after it went to sudden death, the Town captain kept out Connor Kirby's kick to send the home side through.
Grimsby boss Michael Jolley named a strong starting line-up showing just three changes from the team that lost at home to Crewe at the weekend.
Liam Gibson, Mattie Pollock and Ethan Robson came into the XI, with Elliott Hewitt, Jordan Cook and the cup-tied Luke Waterfall dropping out.
McKeown started in goal, with Luke Hendrie, Pollock, Ludvig Ohman and Gibson across the defence.
Robson, Jake Hessenthaler and Elliott Whitehouse were the midfielders, with Green, James Hanson and Moses Ogbu forming the attack.
Hewitt was named on the bench, where he was joined by Sebastian Ring, Ahkeem Rose, Harry Cardwell, Sam Russell, Max Wright and Charles Vernam.
The Mariners started brightly and forced an early corner, altthough they were not able to turn it into a chance in front of goal.
Whitehouse sent a low shot wide from 20 yards on six minutes, before a period of Macclesfield possession saw the visitors look to build attacks up patiently.
A more direct move by the away side saw midfielder Jay Harris drive through the middle before shooting from 20 yards but his low effort was comfortably stopped by McKeown.
A cross from Theo Archibald on the left was headed clear, then Whitehouse became the first to see a yellow card after he brought Theo Vassell down inside the Town half. The resulting free-kick was headed behind for a corner but the short delivery from it was cut out and the Mariners broke clear.
Macclesfield won another corner after an attack down the right on 19 minutes but Connor Kirby's ball was headed away by Hanson.
Archibald beat Gibson down the right soon afterwards and cut inside but fired straight at McKeown, before the keeper was called into action again on 23 minutes when he dived to stop a shot from Connor Kirby.
Another shot from distance flashed wide of the target as Macclesfield continued to have the better of things, before a spell of Grimsby possession ended when a long, cross-field ball was headed clear.
A foul by Hendrie gave the visitors a free kick on the left but after the initial delivery was headed away, Archibald's curling shot from the edge of the box missed the target.
Town had created few opportunities so far but they had a chance on 32 minutes when Ogbu took the ball forward before getting it back from Hanson but volleying at visiting keeper Owen Evans.
Miles Welch-Hayes found himself with the space to cut into the Town penalty area from the right on 37 minutes, although he could only find the Pontoon Stand with his shot.
Green sent a shot across goal and wide at the other end two minutes later, then Kirby fired wide for the away side.
One added minute was played at the end of a half in which Macclesfield had looked the more dangerous of the two sides but neither had managed to force a breakthrough.
No changes were made before the restart and Town had the first chance of the second half, with Whitehouse shooting wide after good play by Ogbu.
Hendrie was spoken to by the referee after a foul on Corey O'Keeffe near the left touchline, level with the edge of the box. Archibald's delivery from the free-kick was too strong though and went out for a Grimsby throw-in.
Town almost took the lead on 50 minutes when Green took the ball forward and found Ogbu inside the box. His shot looked to be rolling towards the net but centre-back Fiacre Kelleher managed to scramble it off the line and away for a corrner.
Hessenthaler was booked for bringing Emmanuel Osadebe down, before a spell of Grimsby pressure led to a foul on Green on the right. Robson was replaced by Wright before the free little over 20 kick was taken but Hessenthaler's ball was headed clear.
Wright went close to giving Town the lead when he set off on a mazy run through the middle and carved his way through the Macclesfield defence but could not get the ball past keeper Evans.
Another opportunity came on 67 minutes when Whitehouse sent a great cross over from the right but Hanson's header at the far post landed on the roof of the net.
Arthur Gnahoua came on for Osadebe in the away side's first change with a little over 20 minutes to go.
Town were piling the pressure on now and a Hesseenthaler corner from the right was headed away, before a shot from Whitehouse went wide after the home side had kept possession and built up another attack.
Archibald hit a shot which flew over the bar at one end, before a Gibson cross was cut out for a corner at the other. Hessenthaler's delivery was headed clear.
Another chance came for Town with seven minutes to go. Hanson won the ball in the air and headed it down for Green but he couldn't generate the power needed to beat Evans.
A Hessenthaler free-kick from the right was put behind for a corner and it was headed away, with Wright's follow-up cross also cleared.
Hanson hooked a shot over the bar as the chances continued to come for the Mariners, who were dominating the game but had been unable to break the deadlock.
Gibson was booked after a foul on the Macclesfield right but Joe Ironside's header from the resulting free kick was easy for McKeown.
The fourth official signalled three added minutes to be played at the end of the game and Archibald shot wide from long range, before Nathan Cameron came on for Kelleher.
Cardwell came on for Ohman and Hewitt replaced Pollock as the seconds ticked down and with the game still goalless at the referee's final whistle, it took penalties to decide a winner.
Green's kick was saved at the start of the shootout as Ironside gave the visitors the early advantage.
McKeown then saved from Horsfall after Hanson scored to leave the scores level again, before Cardwell and Archibald both scored.
Ogbu and Gnahoua both hit the net, before Hessenthaler scored Town's fifth penalty and Evans levelled it up at 4-4.
That meant it went to sudden death and Whitehouse converted to put the pressure back on the visitors. McKeown then made himself the hero as he dived to keep the midfielder's kick out and send Town into the third round and a date at Stamford Bridge.
First though, attention turns back to the league programme, with the Mariners next in action when they travel to Oldham Athletic on Saturday.
- James McKeown (C)
- Luke Hendrie
- Liam Gibson
- Matthew Pollock
- Ludvig Öhman
- Jake Hessenthaler
- Elliott Whitehouse
- Ethan Robson
- James Hanson
- Matt Green
- Moses Ogbu
- Sam Russell
- Elliott Hewitt
- Sebastian Ring
- Max Wright SUB
- Harry Cardwell
- Ahkeem Rose
- Charles Vernam
- Owen Evans
- Miles Welch-Hayes
- Theo Vassell
- Fraser Horsfall
- Fiacre Kelleher (C)
- Connor Kirby
- Theo Archibald
- Jay Harris
- Corey O'Keeffe
- Joe Ironside FW
- Emmanuel Osadebe
- Reice Charles-Cook
- Nathan Cameron
- Eddie Clarke
- Brice Ntambwe
- Ben Stephens
- Arthur Gnahoua
- Virgil Gomis
Attendance: 3011 (44)