Dean noticing that Cas is feeling low - not his usual self, quieter even than before around the bunker. When they talk, Cas hardly ever meets Dean’s eyes. It worries him.
Dean finding a pad of post-it notes in a store he happens to be passing - happens to be passing, he did not spend over forty-five minutes looking - and buying them.
The next morning, there’s Good morning, sunshine stuck to Cas’ bathroom mirror.
The day after that, there’s Give us a smile, sweetheart on the door to Cas’ bedroom.
And the day after that, there’s Turn that frown upside down on the coffee pot. Dean got a little too into that one; there’s a raincloud with a happy face doodled on the corner.
The notes keep going - and every day, Dean watches Cas unfurl a little further, his smile returning by degrees. He looks at Dean with warmth again; he looks relaxed.
Dean writing out one more post-it. One that says something he’s been meaning to say for a while. He doesn’t know where to stick it - where could possibly be the right place or time to read it. After two days of gruff anxiety, he goes to find Cas; he figures he should give it in person.
Cas finds him first. “Dean,” he says. He has a post-it in his hands. “You’ve been looking down. I thought… I don’t know if I’ve done this right. I wasn’t sure…” Dean looks down at the post-it Cas is proffering.
He holds up his own, an exact match, and Cas smiles. “I know,” he says.