Murray Wallace's late, late winner saw Millwall come from behind to secure an Emirates FA Cup shock at The Den on Saturday evening as The Lions defeated Premier League side Everton 3-2.
Richarlison gave The Toffees the lead in the 43rd minute, but in first-half stoppage-time, Lee Gregory headed home to restore parity.
Cenk Tosun then nudged Everton back in front with 18 minutes remaining, but Jake Cooper bundled the ball home just three minutes later to make it 2-2.
The left-back then popped up deep into stoppage-time to secure victory.
Neil Harris made three changes to his starting XI from last Saturday's draw at Middlesbrough - all enforced - as the Cup-tied Ben Thompson and Ben Marshall, plus the injured Jed Wallace, were replaced by Ryan Tunnicliffe, Aiden O'Brien and Shane Ferguson.
Meanwhile, Jethro Hanson and George Alexander were named on the bench.
Just 20 seconds in, with The Den packed out, Gregory fizzed a cross into the box, but it was claimed by England goalkeeper Jordan Pickford.
With eight minutes on the clock, Ferguson's deep free-kick found Cooper, but the centre-back headed well wide. At the other end, Seamus Coleman's cross looked to have found Dominic Calvert-Lewin, but the frontman's swipe at thin air allowed the ball to go to safety.
Four minutes later, another free-kick was sent into the area, this time to the back post where Shaun Hutchinson was waiting, but his header across goal was cleared off the line by Lucas Digne.
Whilst Everton were moving the ball around what was becoming a sodden pitch, with heavy rain falling throughout, the next chance went the way of Millwall, but Yerry Mina was well placed to head Ferguson's cross away from danger.
There was a moment of panic in the Lions defence just under 10 minutes before the break as Jordan Archer sliced a clearance to the onrushing Gylfi Sigurdsson, but Cooper ensured a shot did not follow, shepherding the ball clear.
The Toffees had failed to threaten the Millwall goal up to that point, but two minutes from the end of the first-half, Everton took the lead. The ball found its way to Richarlison, who unleashed an effort from 25 yards out that slipped under the grasp of Archer and into the net.
However, Millwall were not to be denied and in first-half stoppage-time, they drew level. Another Ferguson free-kick was nodded on by Cooper to Gregory, who rose to head beyond the stranded Pickford.
With the second-half just minutes old, Mahlon Romeo's cross found Murray Wallace at the back post, but a moment of hesitancy from the defender allowed Everton to clear.
On 57 minutes, as the rain cascaded down in South Bermondsey, Gregory opted to pass to Shaun Williams rather than take what looked the easier option in shooting, meaning the ball ran out of play. Just before the hour-mark at the other end, Richarlison's ball to Digne allowed the former Barcelona man to cross, but Romeo's crucial intervention stopped a shot troubling Archer.
With 72 minutes on the clock, The Toffees nudged themselves in front once more. Sigurdsson's through-ball found substitute Tosun, who slid a shot in the opposite corner of the net.
However, just as they did in the first-half, three minutes later, The Lions equalised. A corner from Ferguson went all the way to the back post and Murray Wallace - the defender's effort was deflected into the path of Cooper, who bundled the ball into the net despite great protests from the entire Everton team.
With a replay looming large, four minutes into stoppage-time, a free-kick was swung over and converted by Murray Wallace to secure victory - The Lions have pulled off an almighty Emirates FA Cup shock!
Millwall: Archer, Hutchinson, Cooper, Williams, Gregory (Pearce 90+6'), Ferguson (Morison 89'), Romeo, Tunnicliffe, O'Brien (Skalak 86'), M. Wallace, Leonard. Subs not used: Martin, Meredith, Hanson, Alexander.
Scorer: Gregory 45+2', Cooper 75', M. Wallace 90+4'
Booking: M. Wallace
Everton: Pickford, Keane, Gomes, Sigurdsson, Digne, Mina (Zouma 46'), Gueye, Coleman, Calvert-Lewin (Tosun 65'), Richarlison, Lookman (Walcott 79'). Subs not used: Baines, Bernard, Stekelenburg, Davies.
Scorer: Richarlison 43', Tosun 72'
Booking: Gueye, Tosun
Referee: Michael Oliver
Attendance: 16,354 (2,234)