The French striker is currently on loan at Ligue 1 giants Marseille, which will become a permanent stay next summer.
Maupay has endured a disappointing time at Everton after joining from Brighton in 2022.
He scored just one goal in 29 games in all competitions for the Toffees during the 2022/23 campaign.
He was then shipped off on loan to Brentford the following campaign, before being offloaded yet again earlier this year.
The 28-year-old has featured regularly under Roberto De Zerbi in France - helping his side sit second in the table.
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He has been directly involved in six goals from 11 Ligue 1 matches to show Everton what they are missing.
In contrast, Everton are struggling as they sit 16th in the Premier League table - just two points above the relegation zone following Sunday's home defeat to Forest.
And Maupay looked to rub salt in the wounds of Everton fans as he mocked their loss on social media.
Living up to his pantomime villain reputation, Maupay joked on X: "Whenever I'm having a bad day I just check the Everton score and smile."
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It's safe to say that Everton supporters were left fuming by his post, with former WBC cruiserweight champion Tony Bellew simply writing: "P****."
Another X user said: "In our hall of fame for one of the worst players to put on a blue shirt."
Meanwhile, this fan wrote: "Next time you play Everton you're going to get snapped. That will pipe you right down."
His comment drew a response from Maupay, who replied by saying: "See you in the Champions League next season!"
He then followed it up by making a further joke at Everton's expense.
Correcting his previous post, Maupay simply stated, 'Championship,' highlighting the relegation battle the Toffees are involved in.
It's not the first time this season that Maupay has caused the ire of Everton fans.
Prior to his loan to Marseille, Maupay was on the bench for the club's heavy defeats to Brighton and Tottenham.
Following Everton's 4-0 hammering at Spurs, Maupay was one of several players that were targeted with abuse by supporters at a London train station.
In a video that went viral, Maupay appeared to react to the shouts of 'f*** off' from one particular supporter.
He then shared the clip in question on social media, where he said: "Imagine another job where it's normalised to get abuse like this.
"Hanging around at a train station to scream at men who are trying their best…"
And following his recent social media activity, it's safe to say there's no love lost between the player and the Everton fanbase.
Sean Dyche's men return to action with a trip to Bournemouth on Saturday and a heavy defeat could see them slip into the relegation zone.
Following their loss to Forest, Dyche said: "They're all tough games.
"Expectation has probably grown a bit but today we didn't deliver on the expectations. They'll grow again and we've got to go and deliver.
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"Four or five games ago, people were saying, 'Oh, look at this run'. Well, we've turned over a pretty reasonable points return in that run.
"So now the next challenge is, every game is a tough game, I've said it before and I'll say it now."