Southend dumped Carling Cup holders Manchester United out of the competition at the fourth-round stage with a stunning victory at Roots Hall.
Freddy Eastwood's 10th goal of the season made the difference as he curled in a superb free-kick in the 27th minute.
The Shrimpers, who are bottom of the Championship, were saved on numerous occasions by goalkeeper Darryl Flahavan, who denied Cristiano Ronaldo more than once, while David Jones also hit the post for the Red Devils.
Wycombe booked their place in the quarter-finals by beating fellow League Two side Notts County at Meadow Lane.
Wanderers forged ahead four minutes into the second half when a cross from the left was turned into the net by Jermaine Easter for his 12th goal of the season.
Chesterfield's giant-killing run came to an end as they lost 4-3 on penalties to Charlton after a thrilling 3-3 draw at Saltergate.
Addicks goalkeeper Scott Carson saved the Spireites' last penalty from Mark Allott with Hermann Hreidarsson scoring the decisive kick.
The League One side led twice in normal time as first Kevin Hurst's corner from the left was turned home by Colin Larkin after two minutes.
Charlton were level in the 40th minute through Jimmy Floyd Hasselbaink but the Spireites grabbed the lead again two minutes into the second half. Caleb Folan - who scored in their shock victories over Manchester City and West Ham in the previous two rounds - netted his ninth of the season by nodding in Alan O'Hare's corner from the right.
Substitute Darren Bent (73) levelled the scores again less than 10 minutes after replacing namesake Marcus, bundling in a Jerome Thomas cross.
Thomas then supplied the ball in for Hasselbaink to make it 3-2 in the 93rd minute before 38-year-old striker Wayne Allison was credited with Chesterfield's equaliser in the 120th minute.
Under-pressure Newcastle boss Glenn Roeder gained a measure of relief as his side beat Watford in a sudden-death penalty shoot-out at Vicarage Road after a 2-2 draw.
Roeder's men made a dream start when Emre's free-kick into the box was headed in by Antoine Sibierski in the third minute.
However, the Magpies failed to hold on as Damien Francis got on the end of Ashley Young's free-kick from the left in the 69th minute.
Another Young set-piece set up Dan Shittu to nod in Watford's second in the 108th minute but Scott Parker's superbly-taken goal (116) set up the shoot-out. Magpies goalkeeper Steve Harper was then the hero as he saved Jordan Stewart's penalty.