Oh god exhausted Dean in season 5 on Bobby's couch nodding off on Cas's shoulder after a night of insomnia spent talking. Bobby spying them as he quietly comes down for a beer (he's got plenty of shit going on in his head too). Castiel looking with such careful awe at Dean's sleeping face. Oh. So it's like that.
Castiel only flicks his eyes up to Bobby's when he lays a blanket over Dean, and he doesn't change position. Good.
"You taking care of my boy?" Bobby says, quiet as he can without it turning into a whisper (which would definitely wake Dean).
It takes a beat, Castiel's gaze tracking down to Dean, but he answers, "Yes." With appropriate decisiveness.
"He's put a lot of trust in you. We all have."
"Yes. I do not bear it lightly."
"I feel sometimes...I fear our efforts will not be enough. I fear that certain people are becoming too precious for me to lose."
"Welcome to humanity, angel."
Cas shakes his head with a faint smile, suddenly looking more like a guy you might see at the gas station than a celestial being, but then he settles back into austere. "I am welcomed every time I complain. I wish there were less to complain about."
"You and every unlucky sucker on this craphole we call a planet. There's plenty good around too though."
A snuffle from Dean which turns into half a snore into Cas's shoulder get both of their attention, so Bobby only catches a flicker of Cas’s smile before he schools it neutral. The air's so sweet, Bobby's going to end up with toothache if he stays here too much longer.
"He'll thank you to wake him up before Sam gets down," Bobby tells him, and Cas’s nod is serious. Maybe he already knows. How often has this happened? What's that boy been telling him? For his own peace of mind, he adds: "Ain't nothing to be ashamed of, you hear that? Alls I'm saying is to be careful."
Castiel's head tips to the side just a little, and he gets that look Dean complains of all the time, like he's examining the contents of your soul through the eyes. Then he blinks, and they've reached an understanding. "Thank you."
Bobby waves it away, then slopes back towards bed with a final "'Night Cas. Give my regards to Seeping Beauty."
On his way up the stairs, he hears Castiel murmer, "Goodnight, Dean." and he huffs a tired laugh. Maybe they're not going to do too bad out of this Apocalypse after all.