Okay. Here we go C:
I'm making a new cat.
His name will be... oegnfeodimw. [actually, i'm still pondering his name.]
His personality is bubbly and friendly, and later on in life it'll change.
He is in SkyClan.
Okay, onto what you looked here for.
At first, yeah, he's really nice and all. But around mid-apprentice-hood, something terrible will happen, [most likely his best friend will get like, mauled or something. if you want to be his best friend, please state that.] He cares about everyone else more than he cares about himself.
So then, he starts spiraling into darkness, and just kind of becomes the outcast because he changes so ferggin much. [i wouldn't mind him getting made fun of either.] Soon, he'll find a she-cat who's just like him, and they both try to get out of their problems together, thus becoming friends. They will most likely fall in love when they are 'better'.
Yeah, I know it's kind of messy. But he needs a best friend and a friend whom he doesn't know will be like him later on.