Kevin Hart Makes Grand Entrance on Kai Cenat's Stream With Druski

Kevin Hart made such a grand entrance when he dropped on Kai Cenat's "Mafiathon 3" marathon live stream on Monday ... it literally knocked Druski's pants off!

Check it out ... the moment is hilarious AF as Kevin slyly sneaks it between the well-dressed duo chopping it up on the stream with more than a million people watching ... and the two lose their minds!

It gets to the point where Kevin has to tell Druski to settle down -- and pull up his pants -- before he says he wants to redo the entrance with style ... which means dancing to Usher's "Yeah!"

And since it's a classy setting as "Mafiathon 3" concludes today ... KH brought what sure looked like a bottle of Cristal.

The moment was quite a change from what Kai did over the weekend for his stream ... when he took his millions of followers along with him to skydive.

From the close-up shots, Kai -- who was tethered to a professional -- was all smiles as he navigated the parachute to a safe landing, where he was greeted by his crew.