ANON, YOU ARE AMAZING. 

IT’S LIKE HE KNOWS DEAN INSIDE AND OUT SO HE WOULD KNOW IN THE CORE OF HIS CELESTIAL BEING IF THERE WAS JUST A TINY SCRATCH ON DEAN,

(Annoyingly, I think the real reason Cas couldn’t detect Gadreel possessing Sam was because when he was around Sam, Cas was human. Now Cas has angel mojo again he can tell when magic is afoot? But ssssshhhh I like your shipper reason much better. <3 )

ALSO, IMMA WAITING FOR THE FANART IN WHICH CAS STRIPS ALL OF DEAN’S CLOTHES OFF YELLING “DEAN, THERE IS SOMETHING DIFFERENT ABOUT YOU, I NEED TO CHECK WHAT IT IS.” :’)