Celtic – beaten finalists last season – started this campaign with a 2-0 win over sixth-tier Auchinleck Talbot, thanks to goals from Johnny Kenny and Sebastian Tounekti.
They were then drawn against Dundee in the fifth round and were moments away from elimination after Ethan Hamilton’s superb strike gave the visitors the lead. However, Junior Adamu scored a 97th-minute equaliser on his debut to force extra time before Tounekti won it.
Celtic were again made to dig deep in the quarter-final as they needed penalties to beat rivals Rangers at Ibrox.
O’Neill’s side had just one shot in 120 minutes, but won the shootout 4-2 to make it to Hampden.
And there was more drama in the semi-final as St Mirren’s Mikael Mandron made it 2-2 late on to take it to extra time. Celtic’s quality shone through though as four goals in six minutes blew the Paisley side away.
Dunfermline meanwhile started with a 2-1 win over Queen of the South thanks to a Chris Kane double.
They then secured the first of three victories against top-flight opposition as an own-goal from Hibernian midfielder Miguel Chaiwa proved the difference.
Kelty Hearts were dispatched 2-0 in the fifth round, before Matty Todd’s early strike and a double from Olly Thomas earned a superb 3-0 win over Aberdeen.
That booked their place at Hampden, where they beat Falkirk 4-2 on penalties after a goalless 120 minutes.