Left-back Boli Bolingoli was recalled after being left out of the Champions League defeat by Cluj while Christopher Jullien came into the central defence for Jozo Simunovic, who was a pre-match fitness doubt.
Lennon admitted he had preferred Callum McGregor to Bolingoli against the Romanians partly because the Belgian's form had been up and down, but it was Jullien who initially struggled against the Pars in Celtic's 2-1 extra-time win in the Betfred Cup.
The £7 million summer signing from Toulouse allowed Kevin Nisbet the best chance of the first half after misjudging a long ball but the striker could not hit the target with only Craig Gordon to beat.
Jullien went on to make some risky challenges and missed two excellent headed chances, although he proved a real presence in the opposition box.
But Lennon felt both new defenders grew into the game and told them and his team-mates he was proud of their character after James Forrest netted in the 114th minute to stretch Celtic's winning run to 28 games in domestic cup competition.
Lennon said: "They did fine after a wee bit of a shaky start but they came on to a really good game as the game went on, so that will do them a world of good.
"It's a test of character sometimes, not just your footballing ability.
"They have seen great nights, they have seen frustrating games. It's all part of adapting to life here in Glasgow."
Celtic hit the target from 11 of their 36 shots on goal but Lennon was happy to see them take some ambitious strikes as Dunfermline crowded the penalty box.
The tactic paid off when Mikey Johnston netted from 25 yards for the opener before Tom Beadling's goal sparked extra-time.
"Sometimes when you have got that amount of bodies in front of you, you have got to take shots," Lennon said. "I want them to shoot.
"You saw Gerrard, Lampard and Scholes score goals from outside the box and I encourage that from my players. Sometimes it's difficult to play intricately through teams, sometimes a 25-yarder does the job.
"The goalie made some great saves. I don't discourage any of my players taking shots, as long as they have the belief that hit they are going to hit the target or work the goalkeeper, because then anything can happen after that.
"Thirty-six shots, we couldn't have played that badly. I'm not massive on stats but the one stat I do look out for is attempts on goal because if that's round about over 20 then you are doing something right."