Padraig Amond put Newport County in dreamland by scoring the goal that secured one of the biggest FA Cup shocks of all time.
The Carlow-born striker converted a 85th-minute spot-kick to put League Two Newport - 74 places below Premier League Leicester - into the fourth round.
Jamille Matt's 10th-minute header looked like clinching their place only for Rachid Ghezzal to silence Rodney Parade with a stunning equaliser from 30 yards seven minutes from time.
But there was to be another twist and the corrugated iron roof in the main stand rattled - and felt like it would come off - as the final whistle sounded.
This was a classic third-round tie; one to remember; a tie that resonated like that old stand that shook, that rattled, that rolled.
Newport, 13th in League Two, were brave, bold and quite brilliant and went through with a late penalty to make it even more dramatic, even more memorable, even more raucous.
Changes in kick-off times, in team line-ups, in priorities, have all again affected the FA Cup, but this was a tie as good as any in the competition's rich 148-year history.
No one inside Rodney Parade, the second oldest ground in the Football League after Preston's Deepdale, will forget it.
It all went wrong for Leicester once the team-sheets were delivered - not just because Christian Fuchs' surname was spelt incorrectly, with the 'h' replaced with a 'k' in what Newport insisted was a genuine mistake rather than a piece of mischief. Certainly Leicester were left cursing afterwards.
That team-sheet will also provoke much debate among Leicester's supporters and - despite beating Manchester City, Chelsea and Everton recently in the league - this result will add to the questions being asked about manager Claude Puel.
He made seven changes and did not even include Jamie Vardy among his substitutes.
Puel was defiant, claiming that eight of his team had won the Premier League, but none of that should detract from Newport.
There was nothing fortunate about this result. They took the game to Leicester from the start, played with a stunning positivity, defended bravely and then had the belief and reserves of energy to go again after Leicester's equaliser.
Leicester scored in the 82nd minute - just as Tottenham Hotspur did in the fourth round last season, through Harry Kane, before beating Newport in the replay.
Then, Kane cancelled out a goal by Amond, and in a delicious twist for Newport, it was the Irishman who went on to convert the penalty that won this tie.
"I was more nervous taking a penalty against Forest Green a few weeks ago," Amond later said.
"What an opportunity to put the club's name up in lights, to knock out the (former) Premier League champions. This is our chance to be giant-killers. Just make sure you do it."
He did. And so did Newport, who set the tone from the start and scored early.
It was a magnificent goal, with Robbie Willmott tearing past Fuchs and crossing the ball for Jamille Matt to rise above Wes Morgan and guide a header that struck goalkeeper Danny Ward's right-hand post on its way in.
The fans were already straining every sinew just as Matt, a 29-year-old Jamaican striker who has spent his career in the lower leagues, had done in scoring his first goal in eight games.
Newport were unrelenting, and their fans rose to give the players a standing ovation after an injury caused a break in play, and they roared them off at half-time.
Maybe, even before that goal, had come the tie's pivotal moment as Newport goalkeeper Joe Day saved sharply from Rachid Ghezzal with Shinji Okazaki then spurning two good chances.
Ghezzal drew Leicester level with a powerful, first-time rising shot, but Newport hit back.
As teenager Vashon Neufville, on loan from West Ham, and making his debut, crossed the ball, Marc Albrighton inexplicably raised his left arm.
Referee Chris Kavanagh had no hesitation in pointing to the spot and Amond nervelessly the ball home. (© Daily Telegraph, London)