The fierce rivals were drawn to face each other in the last four of the tournament.
Rarely has Twitter been more vibrant after an announcement about a football fixture... to be played in three months!
Controversial opinions exist, of course, about whether this will be the first Old Firm derby since 2012 or the first ever meeting between Celtic and the new Rangers.
But both sets of fans can't wait to lock horns in battle, either way. And some Scottish footballers playing in England have also had their say...
Celtic vs rangers buzzing for this already .....— Robert snodgrass (@robsnodgrass7) November 1, 2014
Just seen the draw Rangers v Celtic. Sure everyone in Glasgow is happy tonight— James Mcarthur (@jamesmcarthur16) November 1, 2014
Even before the draw was made, Rangers boss Ally McCoist had already got into a battle of the minds with Celtic manager Ronny Deila, responding to his claim that 'the best teams are in the SPL' by saying:
"In normal circumstances, he would be right. But in the last few years nothing has been what it seems in Scottish football. We’ve had anything but normal circumstances.
"You have three of the five biggest clubs in the country playing in the Championship.
"That would tell us it’s not normal circumstances. If it were normal then, yes, the three teams in the top-flight would be stronger than the team from the division below. I understand Ronny but I don’t necessarily agree with him."
Just think how intense things will get come matchday... Here are the best fan reactions to the draw on Twitter!
Celtic are going to play Rangers in League Cup semi-final!!!— Raymond J. Stellhorn (@RayStellhorn8) November 1, 2014
Massive game Celtic vs Rangers league cup semi-final. Travel arrangements being checked# old firm#rangersfamily— Robert Samuel (@daftdougal) November 1, 2014
Good draw for Scottish football We the Gers will b underdogs but we can do it Looking forward to a great game 3-2 To the Glasgow Rangers— Stewart (@sc_soly56) November 1, 2014