WARNING: OLSEN THONG AFTER THE JUMP.
Obviously, "whale tail" doesn't refer to fat ass, as evidenced by these thong pictures.
But . . . Mary-Kate Olsen wearing a thong? We dunno, after seeing her in layers upon layers of the finest in oversized designer Grandmawear, we pegged her for more of a Lovepats-briefs-from-the-dollar-store kinda girl.