Jack Harlow Met with Awkward Crowd Silence Teasing #1 'First Class' Song

Jack Harlow is learning the hard way that even a #1 single has an expiration date ... even for a track catchy as his "First Class" hit!!!

The superstar rapper got the deer-in-the-headlights treatment last night while doing his environmental duty as part of the star-studded lineup for Global Citizen's Power Our Planet concert in Paris.

Jack tried to hype up the crowd by rapping the "First Class" opening lyrics in hopes they finish the bars for him.

You know the part that goes, "I've been a 'G' throw up the 'L'..." before going on to spell "glamorous."

Or maybe you don't -- the French crowd sure didn't seem to know what Jack was trying to accomplish, and kind of left him high and dry.

Lucky for Jack, the beat drop of the Fergie sample jolted the crowd's memory.