Nanafushi

Nanafushi was a ninja who hailed from the Land of Valleys. He was set to steal Konoha's secrets. He used the transformation jutsu to disguise himself as Might Guy. As he entered the village, Naruto thought he was the real Might Guy and took him to Rock Lee's dojo. After a few fights the real Might Guy returned and fought Nanafushi (who concealed himself as Rock Lee by using the transformation jutsu again). Then later after finding out who he really was, they took him in to the Fifth Hokage to be detained.