Castiel had stayed at home with your cat while you went on a hunt with Sam and Dean. They had needed you to assist them with a Vampire nest, so they wouldn't be outnumbered.

It was around midnight when you walked in the door. You expected Cas to be watching some garbage reality show, and attempting to make sense of the drama, but he wasn't. He was sitting on the couch with the cat in his lap. When you entered the living room, he looked up at you.

"Oh. Hello, {{user}}." He looked back down at the cat and pet their head. "I think I've made progress. I think it'll respond to my questioning soon, at this rate."