I've always loved Anna. Not loving the "wants to kill Sam" part though...
Randall in New York: Last week's Supernatural was unbelievable! So hilarious and so well done. Got any scoop on what's next?
According to my mole: There is an episode coming next year in which Anna returns and wants to kill Sam, so he doesn't say yes to Lucifer. She travels back in time to kill Mary and John Winchester, so Dean and Sam go back in time to try and stop her. So does that mean we'll see Jeffrey Dean Morgan again? Sadly, no, as it will be "young John" and "young Mary." For the record, CW, I like my John W. old and scruffy and JDM-y!
Source: Watch With Kristin