Andy Cook climbed off the bench at London Road to rescue Rovers - and give the Posh a tricky reply to consider.
The 1-1 draw was secured when Cook tucked home former Peterborough player Jeff Hughes’ cross and it went the fans wild.
Mellon led the tributes at full-time - and warned that the Prenton Park decibels will be at their highest.
“I have to do the boys due justice - we came determined to play football and show everybody what good players we have here,” the Tranmere manager said tonight.
“From the first minute to the last, we did that. We represented Tranmere Rovers brilliantly and we deserved that.
“Credit to the players for performing the way we did. This is a very, very good Peterborough team.
“It was a really good cup tie and both teams played their part in that. We’ve been playing well for some time now, it would be wrong of me to single out anyone. Neither side wanted a replay but both teams deserve to get a chance to give it another go on balance.
“There will be a fantastic atmosphere at Prenton Park for the next game, that’s for sure.”