Still Human

7. Others are merely mirrors of you. You cannot love or hate something about another person unless it reflects something you love or hate about yourself.

Perhaps he likes Casey because he reminds him of himself.

Raphael knows he is a hothead, knows he has anger management issues, and knows he takes great pleasure in beating up others. Casey Jones shares these qualities, and it's something he can relate to, something that he finds reflected back at him from the human world.

It is, perhaps, also why he hates Casey at times, because there are definitely times when he hates those qualities about himself. But most of the time, he shoulders his anger and hotheadedness and makes the best of it, just like Casey does, and he can't help but admire that in the human.

It might also be part of the reason he both despises and admires Karai.

The kunoichi is cunning and strong and full of determination, traits he sees in himself. She's effective and hard-hitting and doesn't let an enemy forget her.

But she also holds anger, deep inside, and when it rears up and breaks the surface she's as scary as he is – according to Mikey, anyway.

Anger is his most defining trait, and it's the trait that he can't figure out. He can't decide if he hates it or loves it. But it's still who he is, and so as he watches others who share his anger he'll try to figure out where it falls on his list of things to like or things to hate.