Listen to Sportsound commentary
Barisic with only goal after Sakala hits upright
Hamilton beat Ross County, St Mirren overcome Dundee & Partick Thistle beat Dunfermline - all on penalties
Kilmarnock strike late against League 2 Dumbarton; Livingston beat Stenhousemuir; Motherwell win at Arbroath; Dundee Utd overcome University of Stirling
Last 16 draw is on Sunday
Celtic v Morton (12:15)
Celtic: Hart, Johnston, Starfelt, Kobayashi, Bernabei, Mooy, McGregor, Turnbull, Abada, Kyogo, Maeda.
Substitutes: Bain, Haksabanovic, Jota, Iwata, O'Riley, Hatate, Forrest, Lawal, Welsh.
Morton: Schwake, Grimshaw, Baird, Ambrose, Strapp, Miller, Gillespie, Blues, Crawford, Quitongo, Muirhead.
Substitutes: Green, Pignatiello, O'Connor, Roy, McGrattan, Garrity, King, Lithgow.
A bumper card yes, but there have been a few casualties with four games off because of the bitterly cold conditions...
These are the postponed ties.
Inverness CT v Queen's Park
Cove Rangers v Ayr United
Linlithgow Rose v Raith Rovers
Elgin City v Drumchapel United
The Elgin and Linlithgow home matches have been rescheduled for next Tuesday (19:45 GMT). The Cove and Inverness games will be on Tuesday, 31 January (19:45).
It's Scottish Cup fourth round weekend and that means the big boys join in the fun, the weather is terrible and we might just get an upset or two.
The Old Firm bookend a busy day, with Celtic hosting Morton in the lunchtime kick-off, which is being shown live on BBC One Scotland, and Rangers at St Johnstone for the late start.
In between, there are eight ties at 15:00.
Image source, SNSWho will get their mitts on the famous old trophy in May?