“If Castiel had not been as incredibly charismatic and as complicated as he turned out to be, we would've grown tired of that storyline and ended up killing him and blowing the storyline off, like we have in the past to other storylines that haven't entirely worked for us. The guy who really deserves the majority of the credit for that is Misha Collins, because he came in and he immediately had such chemistry with Jensen and Jared and was able to hold the screen with them. He was just such the total package in terms of giving a really complicated, interesting, charismatic performance, and you just wanted to know more about this character because of him. Ultimately, it's through Castiel that we view the angel mythology - he's the one that introduced it to us, he's the one who expanded it. Zachariah, Uriel, and Anna fleshed out the mythology, and made it so fun, but the fact is that it all started with Misha's Castiel. I owe him an amazing debt of gratitude for delivering such a wonderful performance and for being a terrific guy and being so easy to work with.”
—Eric Kripke on the angel storyline (Supernatural Companion Guide Season 4)
“As soon as you give them what they want, they're irritated that they're getting what they want, immediately after there's a burst of comments like 'fans controlling the show.' The reality of this business is this is serialized drama. I have the story I'm telling, what all the plotting and conspiracy is leading up to, and I've never deviated from that story, it's been right on since the pilot and that's what matters to me. That's the story I'm telling. Now over the seasons, subplots developed, and some of them work and some of them don't...and if there's a subplot that everybody hates, and even the writers themselves can pick out the flaws, I have no problem dropping it. I think it'd be foolish to hold onto it through vanity and pride. If it's not the main storyline, it's fair game. The fans don't have much power as they think they do, but we will listen, and if it's unanimous and true hatred, not just suspense you love to hate, then if it's a subplot, it's completely negotiable. You pay attention to what people are saying, but you can't have any loud and vocal minority influencing any creative decisions on the show, you just have to pay attention to what's going on and who's saying what.”
—Eric Kripke, interview in Fandom at the Crossroads: Celebration, Shame and Fan/Producer Relationships, by Lynn Zubernis and Katherine Larsen, pp. 179-180.