Clippers Star -- Sir Mix-a-Lot Crashes Wedding ... Raps 'Baby Got Back!'

The entire L.A. Clippers squad got a helluva surprise at Jamal Crawford's wedding this weekend -- when Sir Mix-a-Lot hit the dance floor and busted out a live performance of "Baby Got Back!"

The whole thing was awesome -- besides the surprise performance, nearly the entire Clippers team flew in to Seattle to support their teammate ... from Blake Griffin to CP3 and Matt Barnes.

And the they weren't exactly wall-flowers ... all of the guys hit the dance floor HARD -- showing off their moves in a kick-ass reception that looked more like a scene out of a Hollywood nightclub!

Congrats!