Kakasi has a special eye called the sharingan. It was developed from the eye of the hyuga clan. The sharingan was a bloodline limit ability which should have only been passed down to certain people in the uchiha clan. Kakashi is not from the Uchiha clan so we wonder how he got it it is said to been have surgically put in there, that is why he only has one. You never see it until chapter nine when Zabuza comes and picks a fight with him since gatoh wants to kill the man that kakaskhi and his team are protecting. when he uses the sharingan he is able to do any jutsu that a ninja does in this case it would be the water clone. they fight Zabuza and Kakashi and then Kakashi messes with Zabuzas mind in order to do the water fall technique wich almost kills Zabuza who is left in a near to death state by his companion. Naruto ghets pissed when the little kid about his age "killed Zabuza" and thats the end.