Terry Venables' Premiership big guns Leeds United will face a potential banana skin at Glanford Park after Martin Carruthers fired Scunthorpe into the third round.
Danger man Carruthers burst dangerously through in the 24th minute only to be denied by a brilliant last-ditch tackle by classy Carlisle defender Darren Kelly.
But within 60 seconds Mark Summerbell was booked after he chopped down Wayne Graves 30 yards from goal.
And Carlisle were caught napping as Ian Kilford cleverly threaded a quick free-kick into Carruthers who shot low across keeper Matty Glennon and into the net.
Two minutes later Peter Murphy almost levelled with a stunning 40-yard rocket free-kick that smashed off the bar with keeper Tom Evans rooted to the spot.
Carlisle boss Roddy Collins threw on winger Ryan Baldacchino and striker Brian Wake for the ineffective Paul Robinson and Will McDonagh after the break.
And livewire Wake forced Evans into a brilliant fingertip save with a powerful header from a Kelly cross in the 53rd minute.
Baldacchino floated over a cross 14 minutes later that Murphy volleyed through a crowd of players with no one able to apply a finishing touch.
Carlisle were reduced to ten men in the 71st minute when ex-Middlesbrough ace Summerbell was sent down the tunnel for an ugly sliding foul that saw Graves stretchered off.
Carlisle boss Collins said after the game: "I thought the ref was a bit quick with the card.
"It's a cup game, the ball was played short and both players went for it. My only concern now is getting the players fit both physically and mentally for the game on Boxing Day."Iron substitute Alex Calvo-Garcia should have added a second deep into stoppage time, but after chipping the ball over the stranded Glennon he could only look on in disbelief as the ball dropped agonisingly wide.
Delighted Scunthorpe boss Brian Laws said: "The result was fantastic but the best thing to come out of tonight and that pleases me more than anything is that it means I can tell some of the young players that they've got a job next season.
"It's a fantastic time to play Leeds and they are a quality side. We've been dreaming for years of having a Premiership side at our ground and it will be a spectacle for our fans."