Pierre-Emerick Aubameyang scored on his Arsenal debut but was overshadowed by Aaron Ramsey's hat-trick in a 5-1 Premier League thrashing of Everton, while former Gunner Alexis Sanchez netted his first Manchester United goal on Saturday.
Club record signing Aubameyang immediately rekindled his relationship with former Borussia Dortmund teammate Henrikh Mkhitaryan, also making his home bow, as Arsenal's new-look front line shone, but it was Ramsey who provided much of the end product with his first career hat-trick. Laurent Koscielny was also on target.
It was Sanchez's departure that paved the way for Mkhitaryan's move to the Emirates Stadium from Manchester United, and the Chilean also got accustomed to his new home, scoring as Jose Mourinho's men eased past Huddersfield Town 2-0 at Old Trafford.
Victory moved United to within 13 points of runaway leaders Manchester City, who dropped points for just the fourth time in the Premier League this season in a 1-1 draw at Burnley. Johann Berg Gudmundsson's equaliser eight minutes from time cancelled out Danilo's spectacular opener.
A renewed sense of optimism at Arsenal following not only Aubameyang and Mkhitaryan's arrivals, but also Mesut Ozil signing a new contract, exploded in a four-goal salvo in the opening 37 minutes.
Mkhitaryan teed up Ramsey for an early tap-in before Koscielny bundled home Shkodran Mustafi's flick-on and Ramsey's long-range effort deflected in off Eliaquim Mangala on his Everton debut.
The moment the Arsenal faithful had been waiting for came eight minutes before the break when Aubameyang chipped home Mkhitaryan's through ball and the goal was allowed to stand despite the Gabon striker being offside when the pass was played.
"It is very early, but they look to have the quality to integrate into the game we want to play," said Arsenal boss Arsene Wenger of his new signings.
"They are quick, have sharp movement and agile and want the ball. It is very good and positive signs."
Everton restored some pride after the break as Dominic Calvert-Lewin reduced the arrears before Ramsey completed his hat-trick to move Arsenal back to within five points of the top four.
United Scale 'Berlin Wall'
Mourinho had called on his players to mark the occasion of the 60th anniversary of the Munich air disaster that killed eight of the great United Busby Babes side by bouncing back from Wednesday's defeat at Tottenham Hotspur.
But the hosts had to wait until 10 minutes into the second half to make the breakthrough when Romelu Lukaku volleyed home Juan Mata's cross for his 19th of the season.
"We had to be patient but had to keep the intensity high and the pressure," Mourinho said. "We had to break down the Berlin wall organised so well by (Huddersfield manager) David Wagner."
Sanchez was then given the chance to cap his home debut 21 minutes from time when he was brought down just inside the area by Michael Hefele.
And much to his relief, Sanchez tapped home the rebound after Jonas Lossl had saved his initial effort from the penalty spot.
"It was nice for Alexis Sanchez to win a match, the first at home," added Mourinho. "It was not the goal of his dreams, but it is a goal."
City were made to rue a host of squandered chances, most notably when Raheem Sterling missed an open goal, as Burnley salvaged a valuable point despite seeing their winless league streak extended to nine matches.
"Football is about goals. We needed to score the second, third and fourth when we had the chance. When you arrive in the last 15 minutes at Burnley 1-0, this is what can happen," said City boss Pep Guardiola.
Leicester missed the magic of star man Riyad Mahrez as they drew 1-1 at home against Swansea.
The Algerian hasn't trained since Leicester priced Manchester City out of a move for Mahrez on transfer deadline day.
Southampton earned their first win since November by edging a thriller 3-2 at West Bromwich Albion to move out of the bottom three.
Brighton bagged their first league win in seven games, beating West Ham 3-1, while Bournemouth moved up to ninth by coming from behind to beat Stoke 2-1.