After a disappointing midweek where The Celts crashed out of Champions League qualifying, the home fans turned up in expectation, as they looked to put the hurt behind them, and aim for a fourth successive domestic treble.
Story of the match
Celtic made changes following their 4-3 defeat to CFR Cluj with Craig Gordon replacing the injured Scott Bain in goal, summer signing Christopher Jullien replaced Simunovic in defence. Bolingoli, Bitton and Griffiths also came in with Ntcham, Brown and Forrest all dropping out of the starting line-up.
Dunfermline made two changes, with injured Euan Murray being replaced by Morrison, and forward Andy Ryan replaced by Edwards.
Before the game, a banner from a section of the Celtic fans made their thoughts known on recent decisions and suggested the club are gambling on the potential 10 in a row success.
The mood with some fans wouldn't have improved much in the first half, as Celtic went in at the break on level terms, unable to find the breakthrough beyond the organised Dunfermline defence.
The Pars could have taken a shock lead at Celtic Park, when summer signing, striker Kevin Nisbet finding opportunities in the League Cup holders defence, but he couldn't make them count and the best chanced was stabbed wide.
It was defender Jullien with the chance to send Celtic in with a lead at half-time but he headed over, just after Nir Bitton had hit the post.
Mikey Johnston did break the deadlock when his 55th-minute goal put the hosts in front, but The Pars punched back. Substitute Andy Ryan's cut-back found Tom Beadling, who finished to stun the Celtic support.
Celtic threw what they could at Dunfermline, but there was a nerviness whenever the away side attacked, such was the mood at Celtic Park this weekend.
The full-time whistle was met by boos from the stands, and with six minutes of extra time remaining, dogged Dunfermline were unable to stay strong and James Forrest's deflected shot found the back of the net and finished off the men from Fife.
Takeaways from the match
With them on the bench in the European exit midweek, and an early scare against Motherwell last weekend, the spotlight has slowly cast over to the new arrivals Christopher Jullien and Boli Bolingoli and what impact they will have on the champions this season. Sitting in the dugout for the start of a massive game for The Hoops, and coming into a League Cup tie against lower league opposition at home, neither overly impressed and still appear to be settling at Celtic Park.
Dunfermline were only six minutes away from taking the current Scottish Champions and League Cup holders to penalties in their own backyard. You could argue the result was a cruel blow to The Pars, but they showed superb spirit and resilience and will earn plenty of plaudits after this performance. Manager Stevie Crawford will hope this can prove huge confidence as they aim for Premiership promotion this season.
Player of the Match
James Forrest stepped up for Celtic, just as he has done so much, and if not for his extra-time winner, Celtic could have been facing the prospect of penalties.