THE PERPETRATOR Sir Mix-A-Lot THE PROOF ''Iron Man'' (from 1988's ''Swass'') THE PLEA ''It was a redo of the Black Sabbath tune...absolutely horrible! I guess Run-DMC's 'Walk This Way' got so big that I said I gotta do a rock tune like that... GOD! It was cheesy. I didn't take the rock serious enough. I thought I could throw a guitar in there and all the white kids would be like, 'Yeah!' I totally underestimated the intelligence of my fans. You don't touch classics. That was stupid, but I learned my lesson, I guarantee you that.''