Gone are the days when Sir Alex Ferguson and Arsene Wenger bickered on the touchline, pizzas were frisbeed down the tunnel and Patrick Vieira and Roy Keane were at each other's throats.
These customarily tempestuous clashes were at their fieriest in the early noughties, with the first four years of the new decade seeing United and Arsenal garner two Premier League titles apiece.
During the 2003-04 term, the power had shifted towards north London, though, in a season that saw the Gunners become the first side since 1889 to go an English top division campaign unbeaten.
Yet their closest rivals - United - undoubtedly came closest to ruining an invincible run that eventually extended to a staggering 49 games.
In September 2003, with the game crawling towards injury time at 0-0, Martin Keown looked to have gifted the points to the home side after felling Diego Forlan and conceding a penalty.
Ruud van Nistelrooy assumed responsibilities, facing Jens Lehmann's unorthodox side-to-side movement on the goal line.
Simply put, the Dutchman bottled it. Deciding to strike the ball with power, his effort thumped against the bar with Arsenal players swarming round him in delight.
Keown took that one step further in an incident that remains completely unforgettable in the Premier League - the veteran centre-back screaming in Van Nistelrooy's ear and knocking him with his arm.
The United striker would eventually get his revenge in 2004 when his penalty put an end to Arsenal's unbeaten run and released the demons of the previous year.
By then, however, Keown had hung up his boots at Highbury in securing a move to Reading. Nevertheless, the pair still had time to meet in Arsenal and United jerseys in an FA Cup semi-final in 2004.
And - writing for the Daily Mail - Keown has revealed what he said to Van Nistelrooy at Villa Park.
He explained: "In the 801 games I played for club and country I only saw punches thrown in the tunnel on two or three occasions — and one of them was during a game between Arsenal and United.
"But when I look back, there was always a level of respect between us. United beat us in the FA Cup semi-final in 2004, six months after I had clashed with Ruud van Nistelrooy at Old Trafford.
"I saw him in the tunnel before the game and told him that the incident had not been personal. I’d simply been caught up in the heat of a battle between two great adversaries."
You've got to give props to Keown for this but karma had, seemingly, already been decided. Paul Scholes' goal ruined Arsenal's hopes of a double and placed the Gunners under United thumbs for the proceeding decade.
Which team do you think is the greatest - Arsenal's invincibles or United's treble winners? Have your say in the comments section below.