Keith Curle's men were the centre of footballing attention as they took on the Rams in front of the BT Sports cameras at the PTS Academy Stadium, and they grabbed their big chance to impress.
The match may not have been a classic, and is one the watching neutrals across the UK and beyond will have probably already forgotten about, but for Cobblers and their supporters it was a great night.
And that goes for what happened on and off the pitch.
Led by the stupendous Charlie Goode, Town were the better team than their higher-ranked visitors, who included England's record goalscorer Wayne Rooney in their line-up.
Yes, Derby made a lot of changes, but they did that in the previous round and were too good for Premier League Crystal Palace - well at no point at the PTS were they too good for the Cobblers.
The Rams failed to create a clear-cut chance all night, as Goode and his team-mates worked their socks off to deny them any space at time.
Brixworth boy Jack Marriott, a striker who is deadly when he gets the chance, was left frustrated as he was starved of anything like a sight of goal.
Indeed, the one time he looked like wriggling free of Goode's clutches, in the opening stages of the first half, the Town skipper dragged him to the deck with a tackle that wouldn't have been out of place 500 metres down the road at Franklin's Gardens.
The home fans inside the PTS held their breath and feared the worst, but referee Darren England and his assistant saw nothing wrong with the challenge and played on.
Goode and Town definitely got away with one as it should have been a red card, but they made the most of their good fortune.
Chances for the home side weren't exactly plentiful, but they were the more progressive team throughout and looked the more likely to score with Vadaine Oliver, Andy Williams, Chris Lines and Matty Warburton all going close, but they couldn't get the break they needed in the Derby box.
Off the pitch, it was great to see the PTS packed to the rafters, and the atmosphere was fantastic.
The roads around the ground were gridlocked before the game, and on the walk from the car park to the stadium, you could hear the Cobblers songs loud and proud coming from the fans enjoying a pre-match bevvy or two in the Sixfields Tavern - that's when you know it's a big game.
The support throughout the game was excellent, with the fans feeding off the obvious efforts of the players, and it was one of those nights where the club was as one - and long may that continue.
There was also an emotional moment after 19 minutes as everybody inside the stadium stood to applaud as a picture of Harry Dunn was shown on the big screen. The strength of feeling about what happened to that young Cobblers fan was there for all to see and hear.
The 1,400 Derby fans applauded as well, and they played their part throughout, although by the end of the match the only noises they were making were ones of their frustration at their team's underwhelming efforts.
So, we are now going to have to go through it all again in 10 days or so at Pride Park, and by then both clubs will know who awaits the winners in round five.
Regardless of the draw though, there will be 1,000s of Town fans making the short trip up the M1 for the replay at a ground the club has never played at before, travelling and dreaming of glory.
And if their team can produce another performance like the one of Friday, then those dreams might just be realised... we just need one more sprinkling of that magic of the cup!
Pictures: Pete Norton and Mark Thompson