Disclaimer: I don't own Naruto, if I did, this'd be canon.
Explanation on Everything Kakashi
At the age of ten, Hatake Kakashi was the picture of youth, potential and talent.
There were many ninjas decades older than he was who had not achieved the things he had. He was the son of a formerly great, respected and famous ninja, he was the student of a very great, very honored and very respected ninja and he himself was now a Chunin bordering on becoming a Jonin, with a 100 likelihood of becoming a great and powerful ninja.
At that time, Kakashi was everything a ninja should be, he looked and acted like he was born on the corner of straight and narrow - black hair, black eyes, black uniform, and a smile and face that would make any other ten year old girl swoon.
- -
At the age of ten, Uchiha Obito was the picture of recklessness, unruliness and absolute chaos.
There were many ninjas decades older than he was who had not achieved the things he had. He was almost abandoned by the Uchiha for what he called his 'greatest work of art', in which he vandalised the entire section of the Uchiha section in the village - even managing to sneak into the Hyuuga compound to break their hot water system - and he had managed to cut out a hole into the back of the pants of every single Uchiha police officers uniforms. He was now a Genin, bordering on staying a Genin for life, with a 100 likelihood of screwing over everyone else who crossed his path.
At that time, Obito was everything a ninja shouldn't be, he looked and acted like he was born from being shot straight out of a cannon, and hadn't slowed down since.
And today, Obito created a brand new technique, which was - according to him - the greatest technique ever invented.
- -
Kakashi had just exited a book shop, disgusted with the filth in all of the novels, and was on his way home.
Obito had tailed Kakashi, to demonstrate his new technique on his 'rival' to show him that yes, even Hatake Kakashi could not stop the great Uchiha Obito and his pranks.
Kakashi walked slowly.
Obito dropped stealthly.
Kakashi barely had time to react before Obito unleashed his newest technique onto him.
"ONE THOUSAND YEARS OF PAIN!"
And just like that, the ten year old boy was sent rocketing into the air, eventually crashing into the book store.
Because of that, three main changes happened in Kakashi's life.
Firstly, Kakashi's hair from then on was permanently white, from that one single shock.
Secondly, to repay the shopkeeper of the book store, Kakashi was forced to buy every single erotic novel, and in his boredom, he read them, and soon found he was addicted to them.
And lastly, Kakashi adorned a mask, so no one could ever see such a enormously hilarious shocked expression on Kakashi's face - ever again.
And that explains Hatake Kakashi, in a nutshell.
This is the be all and end all to all Kakashi Origin stories.