This was a really neat episode of Supernatural in general, because it capitalized brilliantly on the two characters whose status quos changed the most irrevocably at the end of season eight — Castiel, who's now human, and Crowley, who also touched his humanity and apparently lost his mojo as King of Hell. They're both in vastly reduced circumstances — which gives us a window into how Heaven and Hell did things in their day, and how they're doing things now. Plus a chance to muse on the nature of humanity, in all its humiliating dignity.
This week, both Castiel and Crowley get foils who perfectly represent everything they no longer are — Castiel is faced with another angel, Ephram, who is the "Hand of Mercy" for Heaven. Ephram has turned serial killer because of his urge to ease people's pain (permanently.) And Ephram tells Castiel that he deserves to be put out of his misery, not just because being human is causing him such great anguish but also because he's given up on all the greatness he once strove for. (As a counterpoint, we hear from Castiel's boss at the convenience store, who asked Cas to babysit for her in a way that totally misled him into thinking it was a date, and tells him he's special because he really cares when her baby has a fever.)
Meanwhile, Crowley has an illuminating conversation with Abaddon, the Knight of Hell who's more or less usurped him at this point — and just like Ephram and Cas, Abaddon tells Crowley he's weak and he's lost his will to greatness. Plus Abaddon is showing a similar lack of restraint to Ephram, massively increasing the yield of souls to Hell by going back on all Crowley's contracts and seizing anyone she can get her well-manicured hands on. We're left wondering if the difference between them is just that Crowley represents an older, more civilized way of doing things — or that he's gone soft. Or both. We catch one last glimpse of him sneaking a syringe of his own blood while Sam watches — as if Crowley wants to weaken himself? Or do a spell?
In any case, not only does this episode open up some fun questions about just how dickish the angels and demons can be before they overreach — it also gets into some neat stuff about what it means to be human. The thing of Castiel dealing with humanity and trying to find meaning in working at a gas station and misinterpreting his boss' attempts to use him for free babysitting as romantic interest is super poignant. So far this season, the fallen angel and the lapsed King of Hell are the most interesting things going on.