National League leaders Wrexham were denied another FA Cup giant-killing as a stoppage-time equaliser from Republic of Ireland defender John Egan ensured 10-man Championship high-flyers Sheffield United forced a replay after an absorbing 3-3 draw.
The famous old Racecourse ground has witnessed its fair share of shocks - with a picture of Mickey Thomas' famous free-kick goal against Arsenal in the FA Cup in 1992 hanging on the wall of the Turf Hotel adjoining the stadium - and this was almost one for a new era at the club.
Watched by one half of their Hollywood ownership duo in Ryan Reynolds, Paul Mullin's 27th goal of the season four minutes from time looked like giving them a victory which was no more than they deserved after going behind after just 64 seconds.
Blades striker Daniel Jebbison's senseless sending-off with 20 minutes to go undoubtedly helped their cause, although they were already in the ascendancy before then, and they duly capitalised.
But just as they were contemplating a place in the fifth round, Egan popped up with an equaliser to take the tie back to Bramall Lane.
It was a cruel blow for the side 70 places below their visitors, second in the Championship, but the performance was a ringing endorsement of the huge steps being made under the leadership of Reynolds and fellow actor Rob McElhenney.
In only the second minute Oli McBurnie slipped his marker Jordan Tunnicliffe to head Tommy Doyle's corner past Luke Young guarding the near post.
In a further blow for the hosts, Tunnicliffe was forced off after getting injured trying to stop the striker and, by the 10th minute, Wrexham had been forced into another change with the second member of their back five, Aaron Hayden, also departing with a calf problem.
Mark Howard saved well in the opening quarter from Jebbison and Doyle but, having weathered the early storm, the home side finished the half strongly and, with a touch more composure, could have got more from their efforts.
The National League side were dragged back into the game by Mullin, who did everything but score in the first half.
Early on he went down claiming a penalty for a foul after racing into Anthony Forde's ball over the top and, while the forward had got the first touch, there was no contact by goalkeeper Adam Davies.
In seven minutes of added time Mullin skipped past Jaden Bogel after Howard's quick release from a Sheffield United corner and his rasping drive was batted away by Davies.
With the last chance of the half he latched onto Chris Basham's attempted clearance under pressure from Ollie Palmer only to be brought down on the edge of the area by Egan, with the Wrexham striker blasting his free-kick into the wall.
Just five minutes into the second half, Davies could only parry Young's long-range shot, creating a scramble from which the visitors hacked out of play.
Another Tozer long throw caused chaos in the box with the ball dropping to James Jones, on as an early replacement for Hayden, off the shoulder of McBurnie and he hooked home a clever close-range finish.
In the 61st minute Tozer followed in his own throw to earn a corner with a deflected shot and Young's inswinging corner hit substitute Billy Sharp in the chest, with Tom O'Connor reacting quickest to lash home.
Celebrations were cut short as four minutes minutes later Oliver Norwood fired home a low effort after the ball had bounced around the Wrexham area.
The visitors shot themselves in the foot when Jebbison was sent off for an off-the-ball clash with Tozer on the halfway line after referee Dean Whitestone took advice from fourth official Scott Oldham.
Palmer crashed a shot against the underside of the crossbar which bounced down inches from the line before Mullin sparked wild scenes when, found in space 10 yards out, he slotted through the legs of the goalkeeper to maintain his record of scoring in every round of the competition, including qualifiers.
But Egan's far-post equaliser from a set-piece spared the Blades' blushes.
When @RMcElhenney and I got into this it all felt so impossible. But impossible is @Wrexham_AFC's favourite colour. That was one of the most exciting things I’ve EVER seen. Thank you each and every Wrexham supporter who came out and aimed your heart at that pitch tonight ⚔️🏴⚔️ pic.twitter.com/s4dbCDJS7W
— Ryan Reynolds (@VancityReynolds) January 29, 2023
Earlier, Stevenage's run in the competition came to an end as they were defeated 3-1 by Stoke in an entertaining tie.
The in-form League Two side, buoyed on by 3,291 travelling supporters, were eyeing passage to the fifth round of the competition for the first time since 2012.
However, their return to the midlands - where they came from behind to upset Unai Emery's Aston Villa in the previous round - was an unhappy one.
The Potters took an early lead inside two minutes through Jacob Brown and assumed control.
Stevenage levelled in the second half through Villa Park hero Jamie Reid, but their reprieve was short-lived thanks to Josh Laurent's magnificent effort and then Lewis Baker added a late third from the penalty spot.
