This is not a spoiler, just a few things I picked up on IMDB's Supernatural trivia page.
1, and personally my favorite piece of information was that
Kristen Bell was originally offered the role of Ruby in the third season,
and she declined. Now, I adored Katie Cassidy's Ruby (damn you fandom crazies for getting her recast), but I cannot help but wonder how K. Bell would have performed. I'm a huge Veronica Mars fan, and zipped through
Heroes just to see my favorite new actor. Elle Bishop had the potential to be a great character, but was mostly disappointing. Ahhhh I think she would have been great in SPN, but she was a serious dumb fuck for turning down the offer.
2, the creator of the series, Erik Kripke had a son born on the same day that was selected for Sam's birthday and thought it was "creepy." I think it's awesome, and maybe just a little creepy.
and 3, Jensen Ackles originally auditioned for the role of Sam... could you imagine?