Celtic manager Martin O’Neill will face his former captain, Neil Lennon, in the Scottish Cup final after the Hoops eventually beat League Cup holders St Mirren 6-2 after extra time in the semi-finals.
Despite racing into a 2-0 lead through Daizen Maeda and Anthony Ralston, Mikael Mandron inspired a heroic second-half comeback by scoring twice, including a dramatic 91st-minute equaliser to take the game to extra time.
However, the record champions fought back in style with a brace from Kelechi Iheanacho and goals from Luke McCowan and Benjamin Nygren, emphatically blowing their opponents away and ensuring there would be no repeat of December's League Cup final.
Hampden Park will now host an emotional finale between two Celtic greats on May 23 after Lennon's Dunfermline Athletic shocked bitter rivals Falkirk with a shoot-out victory in the other semi-final on Saturday.
St Mirren got off to a nightmare start when backup goalkeeper Ryan Mullen was charged down by Maeda, resulting in the opening goal inside the first minute.
The ex-Celtic youth stopper, who was deputising for the injured Shamal George, took a heavy touch before the Japan international pounced and slide tackled the ball into the net.
Mullen's error was compounded 14 minutes later when he pulled up with an injury of his own, meaning 17-year-old Grant Tamosevicius was thrown on for his senior debut.
At the other end, Celtic's Viljami Sinisalo almost produced an identical mistake when he was dispossessed by Mikael Mandron inside his own six-yard box, but the Finland international's blushes were spared as Killian Phillips failed to convert the resulting close-range opportunity.
This came just moments after Sinisalo produced an excellent stop to deny Liam Donnelly's powerful headed effort from a corner.
Tamosevicius didn't appear to be fazed by the occasion; he made a smart save from Maeda and had some tidy moments with his feet before eventually being beaten by Ralston on the stroke of half-time.
The Scotland international thundered an effort in off the bar with the last kick of the first half after stepping onto Yang's clever backheel.
However, eight minutes after the restart, St Mirren were back in it through Mandron.
The striker, who bagged seven on his team's journey to League Cup glory earlier this campaign, headed in Declan John's chipped cross to score for the first time since December.
Celtic then temporarily regained control, though without creating clear-cut chances, before facing a barrage of Buddies attacks in the final 15 minutes.
Sinisalo pulled off an excellent double save in the 87th minute, but couldn't keep out Mandron's second in stoppage-time as the Frenchman latched onto a through ball and belted it into the far corner to send the tie to extra-time.
However, parity didn't last long.
Substitute Iheanacho headed in James Forrest's cross six minutes into extra-time before Luke McCowan calmy rolled in another two minutes later.
Iheanacho then found the top corner in the 100th minute for his second, and Benjamin Nygren completed the scoring shortly after.
Last year's beaten finalists will now face Dunfermline Athletic in a repeat of the 2007 Scottish Cup final - which coincidentally was Lennon's last match as a Celtic player.
Dunfermline boss Neil Lennon insists it will be an "honour and a privilege" to go up against his former manager Martin O'Neill in next month's Scottish Cup final.
Lennon, who played under O'Neill at both Leicester and Celtic, told Premier Sports: "It is quite a daunting prospect. It is going to be a privilege for me.
"It's brilliant to be there in the first place.
"It is a real honour to be there with Dunfermline but to play Celtic, it is the stuff that you would never envisage and it has become a reality.
"I played under him for 10 years. I went to see him in February and said it's 30 years since we first met, in 1996 when he signed me for Leicester.
"We have a brilliant relationship personally and professionally all the way through, it is going to be an honour for me."
O'Neill said of his reunion with Lennon: "I've just done an interview with him. He was doing some punditry work - he gets everywhere.
"But he has done remarkably well. Did brilliantly for me at Leicester and at Celtic and he's done brilliantly at Dunfermline - what an effort yesterday. So I look forward to it."
