Aberdeen took the first semi-final place by beating Kilmarnock.
But their fine win came secondary as Neil Warnock left less than an hour after the game.
You can watch the best of the action from Pittodrie by bashing that play button below.
Just another day in Aberdeen's chaotic campaign.
Video content
Video caption: Highlights: Aberdeen 3-1 KilmarnockHighlights: Aberdeen 3-1 Kilmarnock
Listen live on Sportsound
BBC Radio Scotland
Fancy listening along with the Sportsound gang today? Of course you do.
The team will provide live commentary from Celtic Park and Easter Road in a bumper Sunday show.
Coverage is under way on BBC Radio Scotland.
Nouble and McGovern start for Livi
Celtic v Livingston (14:30)
As expected, Livingston are without captain Michael Devlin after the defender was forced off last weekend against St Johnstone.
He is one of three absentees, with midfielders Jason Holt and David Carson, who is cup-tied, also not even making the bench as manager David Martindale makes five changes in all.
Veteran on-loan Hearts goalkeeper Michael McGovern is preferred to Shamal George, who is joined on the bench by Andrew Shinnie despite the midfielder's goal in Perth last weekend.
Joel Nouble returns to attack, with Jamie Brandon in defence, while Steven Bradley and Stephen Kelly are in midfield.
SNSCopyright: SNS
Stephen Kelly (centre) returns to Livingston's midfieldImage caption: Stephen Kelly (centre) returns to Livingston's midfield
Carter-Vickers misses out for Celtic
Celtic v Livingston (14:30)
Cameron Carter-Vickers, who had returned from injury to play Celtic's latest three games, is a notable absentee, with Stephen Welsh coming into the centre of defence.
The only other change is Nicolas Kühn starting on the wing in place of the suspended Yang Hyun-jun.
Fellow winger Luis Palma had been an injury doubt and does not even make the bench.
SNSCopyright: SNS
German winger Kuhn comes into the Celtic attackImage caption: German winger Kuhn comes into the Celtic attack
Live Reporting
Nick McPheat
All times stated are UK
About yesterday...
Yesterday was a bit wild.
Aberdeen took the first semi-final place by beating Kilmarnock.
But their fine win came secondary as Neil Warnock left less than an hour after the game.
You can watch the best of the action from Pittodrie by bashing that play button below.
Just another day in Aberdeen's chaotic campaign.
Video content
Listen live on Sportsound
BBC Radio Scotland
Fancy listening along with the Sportsound gang today? Of course you do.
The team will provide live commentary from Celtic Park and Easter Road in a bumper Sunday show.
Coverage is under way on BBC Radio Scotland.
Nouble and McGovern start for Livi
Celtic v Livingston (14:30)
As expected, Livingston are without captain Michael Devlin after the defender was forced off last weekend against St Johnstone.
He is one of three absentees, with midfielders Jason Holt and David Carson, who is cup-tied, also not even making the bench as manager David Martindale makes five changes in all.
Veteran on-loan Hearts goalkeeper Michael McGovern is preferred to Shamal George, who is joined on the bench by Andrew Shinnie despite the midfielder's goal in Perth last weekend.
Joel Nouble returns to attack, with Jamie Brandon in defence, while Steven Bradley and Stephen Kelly are in midfield.
Carter-Vickers misses out for Celtic
Celtic v Livingston (14:30)
Cameron Carter-Vickers, who had returned from injury to play Celtic's latest three games, is a notable absentee, with Stephen Welsh coming into the centre of defence.
The only other change is Nicolas Kühn starting on the wing in place of the suspended Yang Hyun-jun.
Fellow winger Luis Palma had been an injury doubt and does not even make the bench.
LINE-UPS from Celtic Park
Celtic v Livingston (14:30)
Celtic: Hart, Johnston, Welsh, Scales, Taylor, Iwata, O'Riley, Bernardo, Maeda, Kuhn, Idah.
Substitutes: Bain, Lagerbielke, Furuhashi, Holm, Oh, Vata, Kelly, Forrest, Ralston.
Livingston: McGovern, Montano, Obileye, Sean Kelly, MacKay, Brandon, Bradley, Nouble, Nottingham, Stephen Kelly, Yengi.
Substitutes: George, Donnellan, Anderson, Sangare, Shinnie, Guthrie, Culbert.
Post update
Let's get to the teams...
First stop: Celtic Park
Celtic v Livingston (14:30)
Three spots remain...
One down, three to go.
Aberdeen took the first place in Scottish Cup last four yesterday, then lost their manager about half an hour later.
Two other spots will be filled by the end of today, with Celtic hosting Livingston before Rangers go to Hibs.
Get comfy, we'll be here for a bit.