Of course, he played with Neymar at Barca - where he formed a lethal trio with former teammate Luis Suarez.
The six-time Ballon d'Or winner has reunited with the Brazilian superstar this season and will be looking to replicate the same success at Barca with his new team, but with the inclusion of Mbappe.
And he's detailed the difference between the French phenom and the Uruguayan veteran.
Asked to identify the difference between 'MSN' and 'MNM', he replied via Get French Football News: "[Laughs] Age, first of all! We were young when we started to play with Ney.
"Now, the young one is Kylian. And then Kylian and Luis are two very different players. Luis is a pure number 9, a lone striker, who's particularly good in the box and is used to scoring lots of goals.
"Kylian likes to be on the ball more, he's a very strong and extremely rapid player, who kills you if you leave any space and scores a lot as well.
"They are both spectacular players, but with very different qualities."
After scoring his first goal for PSG against Manchester City, Messi challenged Neymar and Mbappe to raise their level of play.
On playing with Neymar and Mbappe, he said: "The more we [him, Neymar and Mbappe] play together, the better it will be.
"We all have to progress together and raise our level of play. We played well, we have to give it our all and keep doing so.
"We won an important game against a very big rival, with great players, who were in the Champions League final last season.
"It's an important win for us. We have to keep progressing and work on a lot of aspects."
Featured Image Credit: PA/France Football
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