Robbie Keane came off the bench at the interval to help Celtic overcome Dunfermline 4-2 to book their place in the quarter-finals of the Active Nation Scottish Cup.
Hoops' boss Tony Mowbray chose to leave out star players Keane and Aiden McGeady for the trip to East End Park and it almost backfired during an exciting first half in which the Pars took all the credit for going in to the break level.
After Diomansy Kamara opened the scoring for the visitors, a David Graham strike and an Andy Kirk penalty put the home side ahead before Hoops' striker Morten Rasmussen gratefully levelled two minutes from the interval.
But when Keane came on for Marc Crosas at the start of the second half, Celtic strode away. The Fifers' resistance crumbled in the second half after defender Callum Woods scored an own goal Keane scored from the spot with his first goal for the club to ensure a safe passage in to the next round.
Keane eventually got his first goal for the Hoops in the 67th minute, although he had to rely on a dubious penalty, awarded when he was tackled inside the box by Pars skipper Austin McCann. The Irishman dusted himself down and slammed in the spot kick before taking the acclaim of the Celtic fans behind the goal.
Celtic huffed and puffed, but there were no more goals and after an unconvincing first 45 minutes Mowbray will have been glad to avoid another slip-up.