What's a Sharingan, you ask? It's the lovely eyes he covers up with his headband. The Sharingan is an advanced bloodline eye that allows the user to copy taijutsus, ninjutsus and genjutsu's, and if used probably create illusions. Kakashi can't quite master the illusions yet, but he can do minor things which is illustrated in the fight with Zabazu. This takes a great deal more chakra which Kakashi can't handle though, and if he uses it too much he faints.

However, the Sharingan isn't Kakashi's real eye, as he's not from the Uchiha clan. The lovely scar that runs down his face like a lighting bolt almost is most likely a scar from a surgery to put the eye in. It's supposedly amazing that Kakashi can even use the Sharingan. Yeah, Itachi said so. ^_^ Me love Itachi, even if he made Kakashi feel the pain of being stabbed a million time. It's a Sharingan obsession on my part, it must be.

But how did he get the eye? Well, i have two theories! Bwahahaha.

1. Kakashi was in most probability a hunter nin at one time or another, and he was sent to destroy an Uchiha's clan members body and stole the eye. Of course, i don't konw if he was a hunter nin, but i've seen colored pictures where he wears the outfit, and also wears the Anbu outfit. ^_^;; I wonder what he used to be...

2. Obito might have been an Uchiha clan.... It's possible! Cute black hair in the nifty long, but not to long style! Okay okay, but he might have been. And maybe at Obito's death he took his eye to remind himself of what he's done.