Voila, two serial killers cuddling on a crime scene :3
Dean just broke Cas out of the psych ward, hence the outfit.
Cas wears a collar with a GPS chip (and with a name tag because Dean is a dick), because sometimes he gets distracted and goes for a walk and forgets who he is, like that time when he was missing for two days, until Dean found him under a bridge, curled in a puddle of mud and blood, with four soaked, dead kittens in his arms, and an even more dead guy, hacked into pieces that littered the ground. He told Dean he’d been led here by a moth to save the kittens’ lives, but was too late. Dean’s heart might have broken a bit at those words, but he’s not sure he has one, so maybe it was just a heartburn. After that he found Cas another kitten, a living one this time, and Cas was the happiest person in the world for whole three weeks, until the kitten scratched him too hard and Cas ripped its head off.
Besides I have a serious collared!Cas kink.
(Dean totally booped him on the nose with a bloody finger)