I babysat kids who have a cat named Lassie...so naming a cat Sirius is totally game.

And the whole Hermione dropping out of school thing was just this huge "stick with your friends in their time of need over everything else" deal. And proving that she really is a Griffindor, not just a Ravenclaw. After all, had she been a Ravenclaw, she would have been like, "Sorry, guys, I'm going to school." Griffindors are loyal and crap, though. And anyway, I would have killed JK if she'd sent Hermione back to school, so that would be reason enough to make her drop out. XD