In the original post, I went into a bit of depth about numbers of minority characters in the show. I'm not going to do that again here, but it has struck me that things are quite different in the latest season. While the diversity of main characters is about the same, that's understandable, but I have noticed a difference in the minor characters (ie, those who appear just in one show). There definitely seems to be more variety now and the change strikes me as large enough to appear to be a deliberate move.
Importantly, it's happening in a low-key way - there isn't a plot reason for these characters to be from minority backgrounds, they just kind've are. It's not made into a big deal, it's just a normal thing. They're just like any other character, except their skin is a slightly different colour. Quite often on TV or film, actors from ethnic backgrounds only seem to be chosen when the character has traits that have stereotypically been linked to certain races. For example, when a script calls for a high school nerd, there's a good chance an asian will play the character, 'cos everyone knows all asians work hard at school, right? It's like their culture or something.
So anyway, fair play to the people working on the show. It looks like they've seen the issue and are making an effort to make it better, which is pretty great.
And on the subject of Supernatural, this never gets old: