Arsenal produced an astonishing fightback from 4-0 down to defeat Reading 7-5 after extra-time in a 12-goal thriller, as Bradford dumped out Wigan on penalties at the DW Stadium.
Championship duo Middlesbrough and Leeds saw off Sunderland and Southampton, respectively, while Aston Villa survived a scare against Swindon at the County Ground.
Arsenal manager Arsene Wenger may have to review his assessment of the Capital One Cup as the lowest of his priorities as the Gunners snatched victory from the jaws of defeat in an enthralling 7-5 success over Reading to book their place in the quarter-finals.
The Royals roared into a 4-0 lead as the Gunners, showing 11 changes from the side who edged out QPR at the weekend, were a shambles in defence and all over the field before the interval.
Jason Roberts got the ball rolling with a 12th-minute volley before Laurent Koscielny turned the ball into his own net and young goalkeeper Damian Martinez made a complete hash of Mikele Leigertwood's long-range effort.
Noel Hunt headed home the fourth in the 37th minute to leave Wenger fuming on the touchline, with Theo Walcott's response just before the interval hardly likely to have softened the Frenchman's half-time message to his players.
Whatever he said clearly had the desired effect as the Gunners reduced the arrears further through substitute Olivier Giroud before Koscielny found the net at the right end of the field with just one minute of the 90 to play and Walcott snatched an astonishing leveller in the fifth minute of added time.
The drama continued into extra-time with Marouane Chamakh opening his account for the season in the 103rd minute with a drilled effort from the edge of the area, only for Pavel Pogrebnyak to nod home with just four minutes of added time remaining.
Walcott then completed his hat-trick as he smashed home from close range and Chamakh rounded off the scoring on an unforgettable evening with the visiting supporters in raptures and the home fans numb.
On any other evening, Bradford would have been the headline story, but they will have to settle for a lower billing despite dumping Wigan out of the tournament with a 4-2 success on penalties.
The League Two club, the lowest ranked side left in the competition, will take their place in the draw for the last eight on Wednesday night after Roberto Martinez's men could not breach their defence over 120 minutes.
Southampton were another Premier League side to make 11 changes but they paid the price as Leeds claimed their second top-flight scalp of the Capital One Cup.
Having seen off Everton at Elland Road in the last round, Neil Warnock's men claimed a deserved 3-0 success and could even afford Luke Varney to produce a contender for one of the misses of the season when the game was still scoreless.
Michael Tonge put the Whites in front in the 35th minute and they continued to dominate before finally getting the further goals their domination deserved as El-Hadji Diouf struck late on and Luciano Becchio converted a last-gasp penalty.
Middlesbrough emerged as the victors in their North East derby with Sunderland at the Stadium of Light to ensure the Championship would have two representatives in the last eight.
Scott McDonald scored the only goal of the game six minutes before the interval when he turned the ball home from close range after good work from Ishmael Miller.
Aston Villa survived a scare against Swindon at the County Ground as they allowed a 2-0 lead to slip against Paolo Di Canio's League One outfit.
Christian Benteke and Gabriel Agbonlahor put Paul Lambert's men in control only for teenage substitute Miles Storey to score twice in the space of three minutes immediately after joining the fray.
With extra-time looming, Benteke silenced the jubilant home support as he grabbed his second of the evening to put the Midlands side into the last eight in less than convincing fashion.