Jamie Foxx -- Yeah, I DID Dance Like MJ in My Underwear [Video]

Jamie Foxx -- Yeah, I DID Dance Like MJ in My Underwear [Video]: Jamie Foxx does an AMAZING Michael Jackson impression ... in his underwear ... and TMZ has unearthed the unbelievable footage to prove it. The video was shot at an after-party at Jamie's mansion in L.A. ... roughly ten years ago ... right…