Elmander then rounded Tim Krul to score his opener before Andy Carroll reduced the deficit with a low drive.
From the resultant corner, Williamson had to twice block Bendtner shots at the far post before Krul smartly saved the Dane's third attempt.
An attempted nodded clearance from Ryan Taylor hit his own keeper Tim Krul before going into the Magpies net to give Arsenal the lead.
Davies, who lost his place to Carroll in the England squad that faced France in midweek, sent Krul the wrong way with his accurate spot-kick.
Lawrie Wilson caught the eye with a surging run, although his strike was blocked, while Bostwick's powerful low strike drew an excellent save from Krul.
His sureness of touch which dazzled the Wolves defence last season was again evident when he was played in by Davies, rounded Krul and tapped in.
The 22-year-old had not scored since late August but defeated Krul with a powerful strike after Long and Chris Beardsley worked the ball into his path.
City looked dangerous when they broke and Tim Krul was kept busy by a powerful angled drive from Tevez and a low cross from half-time substitute Emmanuel Adebayor.
The visiting side had hardly had time to adjust to their new shape before Long's strike struck Williamson and deflected into the Toon goal with keeper Krul completely wrong-footed.
The Cumbrians were able to bring in goalkeeper Tim Krul on loan from Newcastle last season while left-back Michael Liddle spent a three-month spell at Brunton Park from Sunderland.
Chris Krul: Giuliani, can you explain why you being a lifelong Yankees fan, that this year, after the Yankees lost everything, you rooted for the Red Sox in the postseason?
But it was Stevenage who capped off a famous night by scoring next as Winn superbly lifted the ball over the advancing Krul after collecting a pass from John Mousinho.
Magpies centre-back Mike Williamson was robbed of the ball by Rosicky in the opening minute and the Arsenal playmaker slid a pass through to Carlos Vela, whose strike was saved by the out-stretched leg of Krul.
Teenage full-back John Flanagan provided a testing cross from the right which Mike Williamson only partially headed clear, allowing Rodriguez to volley a shot from 12 yards that took a crucial deflection off Danny Simpson past keeper Tim Krul.
Matt Taylor's free-kick rebounded off the bar and eventually fell at the feet of Danny Simpson, whose clearance bounced off a Bolton player and into the path of Lee in the box who calmly slipped the ball past Krul.
Tim Krul was kept busy in the visitors' goal and was beaten again in the 31st minute when Ben Tozer gave the ball away and a shot from Posh defender Tom Williams somehow squeezed in at the near post.
The ability to play on the counter-attack played into Arsenal's hands and substitute Cesc Fabregas passed for Bendtner to cut inside and find the top corner with a precise strike before Walcott again raced clear and sidefooted past Krul for his sixth goal of the season.
Bendtner was trotting back from an offside position when Walcott was released on goal by Johan Djourou's clearing header, but the Dane ended up colliding with Williamson as the centre-back tried to intercept the ball, leaving Walcott to dink over Krul to add to Arsenal's lead.
Impressive teenage midfielder Jay Spearing was involved in their two other best attacking moves of the half, firstly forcing keeper Krul into a low save with a 25-yard shot and then later provided a superb pin-point cross from the right which Lucas headed straight at the United keeper from 10 yards out.
Krul was distracted by Craig Eastmond, who might have got a faint touch, as he flapped at a Bendtner header and, when Taylor tried to nod clear off the goal-line, all he managed to do was hit the ball against his keeper as it came off him and went into the home goal.
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