Substitute Matthew Dolan snatched a dramatic injury-time equaliser as League Two Newport kept their FA Cup dream alive with a 1-1 draw against Middlesbrough at the Riverside Stadium.
Daniel Ayala's 51st-minute header looked set to send Tony Pulis' men through to the fifth round as the visitors were guilty of missing a succession of late chances.
But the Exiles' persistence paid off in dramatic fashion as Boro failed to clear a Josh Sheehan cross and Dolan - who started his career at Middlesbrough - poked the equaliser past Darren Randolph.
It was everything Newport deserved after a bright performance which saw Padraig Amond come close in the first minute and Antoine Semenyo missed two glorious opportunities to pull level.
Elsewhere, Ben Whiteman's late penalty handed Doncaster a place in the fifth round of the Cup for the first time since 1956 with a dramatic 2-1 win against Oldham.
Veteran Peter Clarke looked to have denied Rovers with an 84th-minute equaliser after Whiteman's deflected effort midway through the second half had put the hosts ahead at the Keepmoat Stadium.
The result was harsh on League Two Oldham, who gave as good as they got against a side from the division above them.
The Latics hit the post and regularly tested goalkeeper Marko Marosi in an end-to-end second half, only for referee Peter Bankes to spot a late handball which gave Doncaster the decisive penalty.
Oldham then had Clarke sent off in stoppage time after he collected a second yellow card.
It was a straightforward affair for Swansea, who eased into the fifth round of the competition as Bersant Celina came up with a goal to remember in the 4-1 victory over Gillingham.
Oli McBurnie's first-half double put Swansea in cruise control before Josh Rees gave Gillingham hope after the break with a fine header.
But that hope was ended in the most spectacular style as Celina found the top corner from 25 yards, and Barrie McKay added another six minutes from time to see Swansea through to the last 16 of the FA Cup in consecutive seasons for the first time since the mid-1960s.
This was a special occasion for Gillingham's Swansea-born manager Steve Lovell, who played for his hometown club in the 1980s.
Lovell's father was also a Swansea season-ticket holder, but the former Wales forward was denied a happy homecoming as Swansea showed just why there are 34 places separating the two clubs in the league ladder.
Nahki Wells rescued QPR from FA Cup elimination at the hands of Portsmouth as the Championship side came from behind to draw 1-1 at a sold-out Fratton Park.
Pompey took the lead in comical fashion in the 63rd minute when Rangers defender Joel Lynch sliced a Lee Brown cross into his own net.
But Wells ensured a pulsating fourth-round tie went to a replay when he crashed home from close range 11 minutes later after Luke Freeman's corner had caused panic in the home defence.
