LOL You wouldn't happen to be talking about Naruto Shippuden episode 15 right? You do know the part where Kakashi used the mist tech on Itachi is filler right? Never happened in the manga so...
And just in case you don't believe me, here is a link to the episode (check 10:40-11:15 for the part you're talking about):
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And here are the manga pages where the entire episode takes place:
chapter 259 pg 11 to chapter 260 pg 15
Here I'll even give you a head start:
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