Kakashi's Mangekyou in Part 1

[Sagebee]

You know some thing I never thought of is how could he of awakened it he isn't a uchiha and what happened to awaken it

 

[NineSNS]

I don't think he knew he had it(honestly I think kishi just came up with it in pt 2, but for the sake of the thread...)

This is the only answer that makes sense. How can Kakashi call upon a power that he didn't know he had? Remember in Part 1, the wielder almost invariably called out the name of the technique before using it. (That and Kishi didn't think of it until the plot for Part 2 was being developed.)

 

[Kakooli]

He wasn't aware he had it. If he was, he would have turned it on the moment Itachi said that only someone with the same eyes can beat him.