Cas hearing Dean ask if he's God and saying "That's a nice compliment". Hot girl Cas heard that shit and went, "Okay well I'm not but what if I was. What if I swallowed all the souls in Purgatory and then killed every homophobe on earth. What then".
Cas experienced a brief period of powerlessness from mid 5.18 to the end of 5.22, and it bothered him to the point of trying to open up about how horrible it felt to the complete wrong audience (Bobby who was paralyzed at the time and had ZERO patience for Cas being sad about not having super strength anymore and basically told him to nut up and grab a gun). I also think that "You don't have to be mean" comment (given the context of how mean CAS can be) lends to how fragile being powerless made Cas feel. Plus his attitude around Michael and Lucifer. He showed up and he fought, but he was scared in a way we've never seen Cas display plain fear before—not the last time he was confronted with an Archangel—Raphael in 5.04. He knew he could very well die then too (Raphael already HAD killed him in 4.22) but he was stoic about it, threw in a bitchy comment on the way out when Raphael tried to threaten him.
The shock of experiencing what it's like to be human brings revelations on fragility and Sam and Dean's strength in the face of their comparative weakness (something Cas notes to Sam and Bobby in the car in 5.21), but also the desire to never personally re-experience this kind of powerlessness again.


























