David Bellion scored what could be the quickest ever goal netted at Old Trafford to propel Manchester United into the semi-finals of the Carling Cup.
The French Under-21 international's fifth goal of the season, which followed a comedy of errors in the Arsenal defence, was clocked at just 18.6 seconds.
Central defender Johan Djourou slipped as right-back Justin Hoyte squared the ball to him.
Bellion burst through the flimsy Arsenal defence and found the net with a shot which goalkeeper Manuel Rivero Almunia ought to have saved as it bounced off his leg.
After their recent controversial Premiership clash, which became known as "Soupgate" and "The Battle of the Buffet", this was much less incident-packed.
There was an explosive start to the second half, however, after Kieran Richardson reacted angrily to a series of wild lunges by Arsenal's Robin Van Persie in quick succession.
Several of the Arsenal youngsters joined in the fracas and referee Mark Halsey booked both Richardson and Van Persie, a player renowned for having a volatile temperament.
The battle of the shadow squads was shaded by United who paraded eight full internationals, although Wes Brown was the only player who started Saturday's Premiership match at West Brom.
Their extra experience proved decisive as the Arsenal youngsters - only Almunia was over the age of 21 - failed to produce their earlier heroics having claimed the Premiership scalps of Manchester City and Everton.
Chris Eagles and Richardson might have added to United's tally in the opening period. Arsenal's only chance in the first 45 minutes was a Jermaine Pennant free-kick which was turned away by keeper Tim Howard.
This was only one of two efforts Arsenal were able to muster in the 90 minutes as they lacked the forward firepower to hurt a United defence which comprised Phil Neville, John O'Shea, Brown and Quinton Fortune.