Brentford proved to be the party poopers as an Andre Gray brace sent the Championship newcomers on their way to a first win against Millwall in 16 years.
On an afternoon when The Lions wore a unique camouflage kit to mark the 100th anniversary of the First World War and welcomed special guests from Headley Court Defence Medical Rehabilitation Centre, The Bees clearly hadn't read the script.
Gray fired the visitors into a 43rd-minute lead and then doubled their tally on 56 minutes. In a crazy 90-second spell, The Lions hauled themselves back to 2-2 with goals from Lee Gregory (58mins) and then Alan Dunne (59mins).
But there was to be a final, sickening, twist in the tale when Gray whipped in a low cross in the 66th-minute that Danny Shittu inadvertently turned into his own net.
Hard as they tried to muster a third, equalising goal, Ian Holloway's charges could not find a way back and the final whistle was greeted by a crescendo of boos from a frustrated home crowd.
Prior to kick-off the roar of The Den faithful reverberated around the stadium as players from both Millwall and Brentford formed a guard of honour for the guests from Headley Court. Once the ball had been handed over to referee James Adcock and formalities had been completed, the sound of absolute silence silence fell over The Den as a minute's silence was impeccably observed by the crowd.
It was yet another special moment on an afternoon when The Lions players were determined to pay their own fitting tribute - unfortunately Brentford had other ideas.
Mark Warburton's side, fresh from a 3-1 midweek win at Nottingham Forest, were good value for their win with some crisp, attacking play.
From the start, the busy Bees looked to spread the ball wide and utilise the pace of Romallo Jota and Moses Odubajo on the flanks, but it was The Lions who created the first half chance in the opening exchanges.
With five minutes on the clock Gregory - one of four changes to the Millwall team - laid the ball off to Lee Martin, but the latter sliced wide of the target from 18 yards.
Brentford responded and five minutes later Odubajo cut in on the left, shaped to shoot and thankfully lashed his effort a couple of yards past the post.
A powerful 19th-minute run by Ricardo Fuller saw the striker sprint past former Lion Tony Craig on the right and play the ball into the path of Magaye Gueye, whose stinging shot was deflected over for a corner.
From Martin's resulting delivery, The Bees cleared the danger and launched a speedy counter-attack, but couldn't make their numerical advantage pay and Jota fired over.
There was a big let-off for Millwall when Gray took advantage of a lack of concentration in the home defence, only to drag his shot wide with the goal at his mercy.
Brentford were really in their stride now and it took a fantastic recovery tackle from Mark Beevers to avert the danger when Gray broke through and shaped to shoot. Moments later a timely interception by Dunne, who just got his foot to the ball, cleared Alex Pritchard's inviting delivery.
At the other end a rare Millwall attack nearly produced the game's opening goal on 39 minutes. Magaye Gueye slipped the ball through to Matthew Briggs and his cross was met by Martin, whose close-range effort was smartly saved by David Button in the Brentford goal.
That proved to be a rare moment of respite for Holloway's side as The Bees were now in full flow. Their relentless spell of pressure paid off just three minutes before the break when Spurs loanee Pritchard fed Gray, who controlled well before rifling a low shot under the body of keeper David Forde.
The Pritchard-Gray combination sliced Millwall apart for a second time on 56 minutes. On this occasion Pritchard won possession from Gueye and threaded a perfect through ball to Gray who made no mistake with a clinical low finish.
However the introduction of Scott McDonald for Gueye seconds later sparked a crazy spell that saw Millwall score twice in as many minutes. The first goal, following an almighty scramble, saw Gregory get the final touch to Shittu's header, bundling over the line from two yards.
Barely 90 seconds later The Den erupted when Dunne picked up the ball 20 yards out, took a couple of strides forward and arrowed an unstoppable drive into the bottom left corner.
Gregory then rattled the woodwork with a header from Brigg's cross and a shot from Gray looked to be squirmed inches wide after Forde got a hand to the ball as the game really started to hot up.
But it was Brentford who edged ahead on 66 minutes when the unfortunate Shittu, under pressure from Harlee Dean, touched Gray's low cross into the back of his own net.
Back came Millwall again with Fuller and Gregory peppering the Brentford goal, but the duo could just not find the necessary accuracy to make their chances count.
Dunne spurned a glorious opportunity to haul The Lions level with 12 minutes remaining, stealing in unmarked to meet Martin's deep free-kick but he steered his diving header a whisker wide.
Sub Mathias Ranegie, a 67th-minute replacement for Beevers, was guilty of squandering two great chances to level as The Lions pushed on in desperate search of a third goal.
The big frontman first headed Richard Chaplow's cross straight into the keeper's hands before volleying wildly over the bar from 12 yards in the final two minutes with Millwall's final chance of the game.
Millwall: Forde, Dunne, Shittu, Beevers (Ranegie, 67mins), Briggs, Chaplow (Upson, 82mins), Williams, Gueye (McDonald, 57mins), Gregory, Martin, Fuller. Subs not used: King, Woolford, Upson, Webster.
Bookings: Dunne (2mins), Martin (30mins), Briggs (78mins)
Scorers: Gregory (58mins), Dunne (59mins)
Brentford: Button; Odubajo, Dean, Craig, Bidwell, Judge, Diagouraga, Pritchard (Smith, 76mins), Toral (Saunders, 76mins), Gray, Jota (Dallas, 66mins). Subs not used: Bonham, Tarkowski, Yennaris, Proschwitz.
Bookings: Bidwell (36mins), Gray (61mins)
Scorers: Gray (43, 56mins), Shittu (66mins, og)
Ref: J Adcock