Despite the despondency of losing Salah and Firmino, Jurgen Klopp's men never lost faith and were accompanied by a typically raucous Anfield atmosphere on a European night.
Incredibly, Wijnaldum went into the match with only three club goals this season, while all the 28-year-old's Champions League goals in his Liverpool career have come in the semi-finals after he also netted against Roma last season.
Origi scored early in the first half, and then scored late, with Georginio Wijnaldum netting twice in between.
Liverpool FC's memorable European night was complete when Origi scored a victor with 11 minutes to go following Trent Alexander-Arnold's quick corner.
The home-side staged one of the most sensational comebacks in the history of Champions League to reach the finals of the tournament for a second successive time.
"The people from outside, they doubted us and thought we couldn't do it", Wijnaldum said.
Liverpool fans believed in the ability of their team and they all came out to sing the lads to victory. "It's wonderful. We knew that at Anfield we could do something special".
Houllier, who led Liverpool to UEFA Cup glory in 2000-01, beating the Catalan giants in the last four, claims he always backed the hosts to upset the odds and felt the stage got to Barca.
The Liverpool players responded, taking the game to Barca and then grabbing a seventh-minute lead when a poor headed clearance from Jordi Alba fell at the feet of Jordan Henderson, who burst goalwards.
It was a brilliant result for Liverpool but also a fantastic performance that was typical of the way they have played all season. Quite the opposite in fact.
It was a insane match to say the least, and, thanks to Wijnaldum, Liverpool is heading to the June 1 final.
Liverpool head for Madrid at the end of the month, and before that their fans will be able to give their team one hell of a send-off.
Mark Lawrenson was speaking to BBC Sport's Chris Bevan.