Sam and Dean go on a hunting trip and something weird happens to Sam, letting see angel's wings.
Sam starts to notice that Cas only spreads his wings out near Dean, Sam wants to get to the bottom of this and fast.
Okay but I just needed to say:
I read the description and literally yelled "WING BONERSSSSS"
Cas be like "B*tch get your slutty af hands off mah boi I called dibs so piss the f*ck off *sassy finger snap*"