Itachi's One True Weakness.
Uchiha Itachi was at first glance, a completely level headed shinobi of the hidden leaf when he was still part of Konohagakure no Sato.
Though unbeknownst to most people outside of his immediate family and best friend, Uchiha Shisui, he had one very crippling weakness... Cats.
Whenever Itachi came across a cat he would always freak out and start trying to find a quick way out of what ever situation he was in just to get rid of the cat and save his reputation.
Itachi's younger brother, Sasuke, somehow managed to witness one of Itachi's moments when he had been only a foot away from a cat.
Said feline was something to be scared of in its own right, being the Fire Daimyo wife's cat, Tora, it had earned a reputation as being "The Demon Cat of Konoha" though for someone like Itachi... the cat just plain scared the complete hell out of him.
Sasuke, seeing this thought up a devious plan, taking a leaf out of Uzumaki Naruto's book, decided to play a few pranks on his older brother.
The next morning was the same as it always was for a certain Uchiha prodigy. The sun was shining through the curtains hung in front of his window, there was a gentle breeze blowing outside producing the ever present shower of leaves that Konoha was known for, and there was a cat on his bed right in smack dab on his chest.
It took Itachi a few minutes to register that last piece of information due to his still sleep fogged mind. Though when it finally hit him, needless to say the entire Uchiha district was woken to a very shrill scream and numerous smashing sounds of glass, wood and other breakable materials.
Sasuke, waking up to his brother's scream, couldn't help but laugh as hard as he could with out falling on his butt. It was a good five minutes before he could stop laughing long enough so he could shower and generally get ready for the day ahead, though one thing was for sure... that training with Itachi today was going to be extremely entertaining for the young Uchiha,