This might sound like one of those, "LOL LOOK I FOUND A MESSUP IN T3H PLOT!11", and it kind of is, but I'm actually curious.
I was flipping through channels one day and a Naruto marathon was on Cartoon Network. (Yeah, a marathon! Believe it!). In any case the particular episode I turned to was way back in the Land of Waves, when Kakashi was fighting Zabuza (before the fight on the bridge).
Well, Kakashi was using Obito's Sharingan and seemingly got behind Zabuza and had a kunai to his neck. But lo' and behold, it was actually a Water Clone! And Zabuza came at Kakashi from behind!
The Sharingan can see through Genjutsu such as clones etc... Was Zabuza just so awesome he could fool the Sharingan? Can the Sharingan not see through... certain Jutsus like Water Clones? Or was this just a little mess-up in the plot?
Either way, I doubt this was deliberate. But many of you guys here seemingly worship the manga so you might actually know an explanation for that. =)