The dancing feet of Bukayo Saka, the coming of age of Eddie Nketiah, the groans from Manchester red and blue. If this is to be Arsenal's season, then this was a day they'll not forget in a hurry.
A 90th-minute winner from Nketiah, his second goal of the game, settled a modern classic in this great rivalry. Manchester United gave so much to the game, but Arsenal were outstanding and truly worthy winners. It was 3-2 in the end, and the roars of "Eddie, Eddie" were music to the ears of Nketiah and his manager, Mikel Arteta.
What spirit it was that carried the home players. Feeding off a crowd that believes in them, that senses a championship is incoming, the end of a 19-year wait, Arsenal never stopped driving forward, and finally United cracked.
With a 3-1 win at Old Trafford in September, United had already seen to it that this Arsenal cannot follow in the footsteps of the 2003-04 'Invincibles' and go unbeaten through the Premier League season.
But that remains the only defeat the Gunners have had through 19 games, while this was a fifth loss for United, for whom the title is probably now out of reach, their resurgence having hit a bump in the road.
This was the day when Cristiano Ronaldo made his Al Nassr debut, and we witnessed again how United are better off for being without him, Marcus Rashford hitting another exceptional goal for them. Yet United's newest central striker, loanee Wout Weghorst, was largely quiet, while Antony on the right flank flattered to deceive, and you did not need to look far for a stark contrast.
Nketiah, trusted now by Arteta as a frontman for the big occasion, prowled and hassled United's defence and got his rich reward, while Saka's twinkling toes had Luke Shaw in trouble all afternoon long. Saka hit the goal of the game, while Nketiah poached twice from point-blank range.
Saka became only the third Arsenal player to score in three consecutive Premier League appearances against United, after Freddie Ljungberg and Thierry Henry, those Gunners greats of yore, heroes of Highbury.
They've not celebrated a Premier League title since moving to Emirates Stadium, and this particular race is only half-run, but 50 points from 19 games is some start, putting Arsenal five points clear of Manchester City, and they have a game in hand to boot.
Saka had begun to prowl with intent before the breakthrough came, and it went to United, with Rashford sidestepping Thomas Partey and driving a stunning 20-yard shot into the bottom-left corner.
That was a ninth Premier League goal of the season for Rashford, and he has nine in all competitions since returning from England's World Cup campaign, the most of any player from Europe's big five leagues.
United had not lost after scoring the opening goal in a Premier League game since October 16, 2021, when they went down 4-2 to Leicester City, so this boded well. Yet the 26-game unbeaten streak in such games would soon be in peril.
Nketiah got in front of Aaron Wan-Bissaka to head Arsenal level in the 24th minute, with Granit Xhaka's cross from the left giving the Swiss midfielder his fifth assist of the season.
Arteta, furious Shaw was not booked for a challenge on Saka as that battle heated up, later took a yellow card for his troubles.
Arsenal then roared ahead in the 53rd minute, and it was Saka at his majestic best, one-stepping with the ball at his feet on the right, teasing Christian Eriksen before letting fly with his left foot from 25 yards and fizzing the ball into the far bottom corner.
It was Saka's seventh Premier League goal of the season. He'll be going some to better it.
Up to this point, the watching Gareth Southgate would have been enjoying the contest, but England's manager would not have liked the sight of Aaron Ramsdale flapping at a corner soon after, giving Lisandro Martinez the chance to loop in the header that brought United level in the 59th minute.
"This is retro Man United-Arsenal," bellowed Gary Neville on Sky Sports.
Manchester City must have been loving the look of the 2-2 scoreline between their top-four rivals, with City's earlier 3-0 trouncing of Wolves closing the gap at the top, but Arsenal weren't finished. Saka went close, his strike flicking off Eriksen and clipping the outside of the right post.
Arsenal had 69.9 per cent of possession from the 60th to 75th minutes, staking out their prey but unable to make the kill.
They summoned Leandro Trossard in the 82nd minute, the new arrival from Brighton and Hove Albion entering the fray in place of Gabriel Martinelli.
Shaw was booked in the 83rd minute for getting close enough to Saka to stand on the winger's left foot, and from the free-kick Arsenal developed a glorious chance. The ball came through a thicket of players before reaching Nketiah, whose shot was brilliantly pushed wide by David de Gea.
Heads might have gone down in a previous season, but this time Arsenal kept pressing forward.
And then, in the 90th minute, came their reward. Zinchenko's cutback found Martin Odegaard, and with Fred for close company the captain bundled the ball on for Nketiah to toe in from four yards.
90 - @EddieNketiah9 is the second @Arsenal player to score a 90th minute winner against Manchester United in the Premier League, after Thierry Henry in January 2007. Fourteen. pic.twitter.com/CorwCmg7ed— OptaJoe (@OptaJoe) January 22, 2023
Alex Ferguson and David Beckham had taken their seats at Emirates Stadium in the hope of watching United's rejuvenation gather pace, but instead Arsenal put them in their place, clinching a sixth win in their last eight home league games against the Red Devils.
United are perhaps a season behind Arsenal in terms of emerging from years of gloom.
Erik ten Hag's team are not far away, but here they encountered something approaching a finished product. A north London derby win has been followed by victory over United, and it won't be easy street for Arsenal from here on, but once you clear those hurdles, why fear anything?
Which is one way of saying: it's Manchester City next, on Friday, in the FA Cup. Pass the popcorn.