Salt-N-Pepa's 90s Fest appearance was a serious hit for Pepa ... who took a NASTY fall while trying to bust out some daredevil moves on a wet stage.
The rap duo was performing Saturday night in Brooklyn, and while "Sweet Child O' Mine" was blaring ... Pep tried jumping between speakers at the front edge of the stage.
She did NOT make it very far.
Gotta give her props though ... Pepa popped up quickly -- and she tells us she walked away with just a few bruises on her legs.