The Bees went a goal ahead at the Tottenham Hotspur Stadium on Wednesday night when Maupay bundled the ball into the net.
While Ivan Toney's effort was saved, Maupay was there on the follow-up to tap in ahead of Cristian Romero and open the scoring for the Bees.
And in classic Maupay fashion, he taunted Spurs by running off and copying Maddison's celebration.
In front of the fans, he pulled out a dart-throwing celebration that Maddison has made popular this season.
And the Tottenham star was not happy, racing up to Maupay and slapping him on the back of the head.
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Maupay reacted by slapping Maddison on the chest in quite an awkward altercation between the two.
The England international is making his first start for Tottenham from injury after a lengthy lay-off.
Brentford had started the better side in north London on Wednesday night with Spurs leaving huge gaps in behind.
Ange Postecoglou has become a stickler for a high line, even to Tottenham's detriment at times.
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That proved the case when Toney was released on goal but still had plenty of work before he reached Guglielmo Vicario in the Spurs net.
While his powerful effort was saved well by the Italian, he parried the shot into the box where Maupay lurked.
Cristian Romero was not quick enough to react as the former Everton star latched onto the rebound before trolling the home fans with his celebration.
And it is not the first time that the Frenchman has made enemies in this part of London.
Maupay, who scored his fourth goal of the season on Wednesday, notoriously infuriated Arsenal on more than one occasion.
That included an incident that saw Matteo Guendouzi grab his countryman by the throat, which turned out to be his last appearance for the Gunners.