Rae Sremmurd Fave Mannequin Challenge Is the White Beatle's

Rae Sremmurd's making big moves as everyone else stands still to their #1 hit ... and they're calling out other celebs to take their famous challenge.

We got the Black Beatles -- Swae Lee and Slim Jxmmi -- dishing on their favorite Mannequin Challenge takes so far. Sounds like OG Beatle, Paul McCartney, takes the cake -- but they also named some great runners-up ... shout-out to FLOTUS!