Swindon, Northampton, Gillingham and Crawley all claimed Championship scalps in the first round of the Capital One Cup on Tuesday, with last season's finalists Cardiff among those to fall.
There were second tier success stories, though, with Birmingham, Crystal Palace, Ipswich and Leicester safely through.
Cardiff took an early lead against Northampton, but were pegged back by David Artell and Alex Nicholls as the Cobblers secured a notable 2-1 win.
Swindon will also be competing in League One this term and will take plenty of heart from a 3-0 win over Brighton, with Paul Benson and Alan Navarro (twice) on target for Paolo Di Canio's side.
Gillingham made light work of Bristol City at Ashton Gate, with a Danny Kedwell penalty and a second-half effort from Ben Strevens seeing them to a 2-1 victory.
There were no such troubles for Darren Ferguson's Peterborough, with four different scorers finding the back of the net in a comfortable 4-0 waltz past Southend.
Leicester also netted four times without reply as they swept past League Two promotion hopefuls Torquay at Plainmoor.
Burnley fell behind inside 10 minutes against Port Vale, but came storming back to claim a 3-1 win and book their place in round two.
Birmingham's first game under new boss Lee Clark saw them in free-scoring mood, with Marlon King, Darren Ambrose, Steven Caldwell, Peter Lovenkrands and Wade Elliott on target in an emphatic 5-1 victory over Barnet.
Kagisho Dikgacoi grabbed what proved to be the winner for Crystal Palace as they came from a goal down to see off Exeter 2-1.
Ipswich also trailed at one stage against Bristol Rovers, but saw Jason Scotland, Tommy Smith and Aaron Cresswell dig them out of a hole.
Stevenage eased their way past AFC Wimbledon, with three goals inside the opening 45 minutes seeing them wrap up a 3-1 win before the break.
A stoppage-time penalty from Kevin Kilbane saw Coventry edge past Dagenham 1-0.
Plymouth prevailed 3-0 in a South Coast derby with troubled Portsmouth, with Pompey only able to name three players on the bench.
Richard Hinds bagged a brace for Yeovil as they put Colchester to the sword, with a 3-0 win taking the Glovers through.
Chesterfield and Tranmere failed to produce a goal in 90 minutes, but managed three in extra-time as a last-gasp effort from Abdulai Bell-Baggie saw Rovers to a hard-fought 2-1 win.
Four games went the distance, with penalties required to find a winner.
No doubting that the most entertaining of those ties came at Pride Park, with Scunthorpe somehow hitting back to draw 5-5 with Derby before winning 7-6 on spot kicks.
Crawley left the Den having sent Millwall packing, with the League One new boys holding their nerve to win 4-1 in a shoot-out after the two teams had ended the game locked together at 2-2.
Oxford played out an uninspiring 0-0 draw with Bournemouth, but will take their place in the next round after winning 5-3 on penalties.
Charlton were held to a 1-1 draw by Leyton Orient at The Valley and became the final Championship side to tumble out on a busy night of cup action as the visitors claimed a 4-3 shoot-out success.