Not content with coming from two goals down to stun Chelsea in the previous round, Bradford followed up Sunday with a 2-0 victory over Sunderland at Valley Parade.
An early own goal from John O'Shea and a Jon Stead strike on the hour mark helped continue Bradford's fairytale cup run in a pulsating fifth round tie.
Stead was scoring for the fifth straight round as the underdogs reached the last eight of the FA Cup for the first time since 1976 -- just one win away from a semifinal and a return to the famous Wembley stadium.
It is not the first time the Bantams, under the management of Phil Parkinson, have caused cup upsets against EPL opposition, reaching the final of the 2012-13 English League Cup before losing 5-0 to Swansea at Wembley.
Bradford was then in the fourth-flight of English football and has since been promoted to the tier above, but still ranked 37 places below Sunderland.
It did not show as Billy Clarke's third minute shot took a wicked deflection off former Manchester United star O'Shea to leave his side immediately on the backfoot.
Sunderland finally woke up and manager Gus Poyet and his bench were furious when Steven Fletcher had penalty claims turned away after going down under Rory McArdle's challenge.
England international Adam Johnson twice went close to an equalizer, but it was his defensive mistake that allowed Stead to score the crucial second goal.
Later Sunday, Arsenal continued its defense of the FA Cup with a comfortable 2-0 home win over second-flight Middlesbrough as Olivier Giroud scored two goals in quick succession in the first half.
The Gunners might have added to the tally after dominating the tie, but Boro, chasing promotion to the EPL, had an effort hit the woodwork in injury time.
Aston Villa, with new manager Tim Sherwood in attendance, had a welcome distraction from its league woes with a 2-1 win over fellow EPL relegation candidates Leicester City.
Saturday's action saw a shock 4-1 defeat for Stoke at Blackburn, while Liverpool, West Bromwich Albion and Reading also reached the quarterfinals.
Louis Van Gaal's Manchester United will complete the fifth round action at third-tier Preston Monday.
In Spain, Lionel Messi marked his 300th La Liga appearance with a hat-trick as Barcelona beat Levante 5-0.
It was his 23rd career triple in La Liga -- drawing him level with Cristiano Ronaldo -- and took him to 26 league goals for the season.
The Nou Camp victory also leaves Barca a single point behind arch-rival Real Madrid in the title race with third-placed reigning champion Atletico Madrid staying seven points adrift with a shock 2-0 defea later Sunday against Celta Vigo.
Brazil's Neymar had given the Catalan giants an early lead, connecting with a Messi cross as his mishit volley found its way into the net.
Messi doubled the advantage just before halftime and took the game out of Levante's reach with his second on the hour mark.
He completed his hat-trick from the penalty spot after Neymar had been fouled and Luis Suarez came off the bench to score a superb fifth.