Trailing 2-1 with just three minutes remaining, Shaun Whalley equalised for the Shrews before wing-back Jack Grimmer headed in sub Scott Vernon’s cross on 97 minutes.
“I just think it was a terrific day for the football club,” said Mellon.
“We know how much this town loves its football and to feel the ground rocking like that...
“To have this club involved in games like this and challenging big clubs like Sheffield Wednesday to get into the fifth round of the FA Cup is what it always should be and we’re very, very respectful of that.”
Tony Pulis slammed his side’s defending after West Brom were held 2-2 at home by League One Peterborough.
Pulis said: “It’s disappointing but that’s cup football. I don’t want to give any discredit to Peterborough, they were brilliant and worked hard and kept going, but I didn’t really have my heart in my mouth at all.
“We’ve been undone by two long, diagonal balls.”
Peterborough boss Graham Westley, who sprung an FA Cup surprise at Darlington with Farnborough in 2003 and five years ago masterminded Stevenage’s shock win against Newcastle, thinks the draw at The Hawthorns will give his players confidence.
“It’s right up there (with the Darlington and Newcastle games) right now,” said Westley.
“But I think the most pleasing thing is that a lot of young players have really grown up this afternoon and got some self-belief.
“They have gone toe-to-toe with some serious players and worked really hard and it gives you the self-belief you can take with you for the rest of the season — the rest of your career.
On-loan Arsenal striker Chuba Akpom hit a hat-trick in Hull’s 3-1 win at Bury.
Bolton boss Neil Lennon admitted his side was ‘too passive’ in the 2-1 home defeat by Leeds. United’s French midfielder Souleymane Doukara grabbed his fourth goal in five games.
“If we had signed this kid from the Premier League for four or five million and he had played the way he has in the last five or six weeks, people would be saying ‘what a steal,’ said Leeds manager Steve Evans of Doukara.
Blackburn manager Paul Lambert got his wish for a Premier League club in the fifth round after Rovers easily overcame League Two Oxford 3-0.
“Oxford are a good side, they beat Swansea in the last round and they are doing well in their league. Now if we got a Premier League side away in the next round, it would help us even more, financially,” said Lambert.
Blackburn now face Liverpool or West Ham.
After a 4-0 win over Walsall, Reading manager Brian McDermott spoke of his affection for the FA Cup. “I love the competition,” McDermott said.
“We got to the semis last season and what a great day out that was.
“We had 40,000 fans there. What’s not to love about it?”