If Castiel's going to be a hunter and tag along with the Winchesters, I imagine he's probably going to share a motel room with them-and since angels don't sleep, I got to thinking about what he might get up to. This didn't go anything like I imagined it would, but hopefully you like it :)
He doesn't always stay in the chair.
He's there when they go to sleep, of course. He's there when they wake up. When they open their eyes in the middle of the night, eyes flitting to the darkest corners before they close once more, he makes sure that he's in the chair then, too.
But he is rarely, if ever, in the chair.
Sometimes he sits at the foot of Dean's bed and watches the television on mute. But the whine of the screen agitates the boys sometimes, so instead he sits at the foot of Dean's bed and imagines it. The sitcoms. The late-night humor shows that he has yet to see the point of. The endless demonstrations of cheap human devices.
When that has lost its charm—which is does, inevitably—he reads the research they've left out on the table. Sam has something of an unofficial journal on his computer, and Castiel has read this at least once a night since he discovered it. It is immaculately researched, and it is interspersed with commentaries such as "Creeps the hell out of Dean." Castiel finds such commentaries useful.
These activities rarely carry him until morning, even though the boys do not sleep long, or very well; so he takes to listening to Dean's dreams—and regrets this decision almost as soon as he makes it. Dean does not dream. Dean has nightmares, one after another, in violent and strobe-like luminosity; now that Castiel has tasted them, they find him in the dark, and become his nightmares too. Sometimes they are about Sam. Sometimes they are about the things Dean has killed, the things that traipsed too close to human, but were dispatched anyway. Sometimes they are about Hell, or about Purgatory. Dean has seen many things that lend themselves well to nightmares. But most often, they are about Castiel; the image of the water closing over Castiel's head, a blood-stained trench coat, a thousand and one images, lightning-quick, of the expression on Castiel's face when Dean discovers that his friend has betrayed them. And scenes of Purgatory, of Castiel giving up—and of empty prayers to an empty night sky. For Dean, there are no dreams, only the sweet respite of blackness, and so that is what Castiel gives him.
Once the boys are asleep, just before the nightmares creep out, Castiel crouches down beside Dean's bed. He can feel them begin to stir. Dean can feel it too, asleep though he might be; his hands flex against the sheets, wishing for a weapon. Castiel wishes he could take them entirely—erase them, feed them back to the darkness, but to destroy them would take more power than he has ever had his hands on. But it does not need to be complicated. He discovered this solution by accident; out of desperation, really. When the nightmares come, he reaches out his hand.
The first time had been the worst: Dean had begun to thrash a little in his sleep—no small wonder, the nightmare had put out beads of sweat on Castiel's own forehead—and Castiel, unsure how he could stop it, had reached out a hand to wake Dean up. But he stopped short, thinking of the explanations he would have to give, the expression on Dean's face as he said, "You did what?" And then his hand, hovering a hairsbreadth from Dean's, was seized suddenly. Not as two people hold hands, fingers interlaced, but the way a child takes the hand of an adult, fingers all pressed together. And the nightmare faded to nothing.
So now Castiel reaches out his hand, and waits. There is never a night where Dean fails to take his hand. When the nightmares have faded, true sleep takes Dean back, and his fingers release. Castiel finds himself powerfully reminded of a soul, deep within Hell, turning to look at him, and the overwhelming sensation of gratitude—of love—for this shining creature which had come to rescue it. Castiel remembers how surprised he had been, how taken aback, that any soul could feel emotions such as these while buried beneath fire and brimstone. But then, it seems the Winchesters exist solely to take Castiel by surprise.
Dean awakes cheerful. He mumbles something into his pillow, and his brother, like some disconnected extension of self, inevitably mumbles something back, a meaningless garble from the depth of sleep. One of them—usually Dean—opens his eyes, begins to shift and stretch, eventually lets out a sigh and sits up; Sam copies him a moment later, in almost an identical configuration, until they're both sitting up and rubbing their eyes. Castiel finds this is a symptom of good sleep, and not habit. Before, the nightmares would wake them up, propel one of them from bed sooner and leave the other for uncharted hours. And Sam, Castiel finds, will sleep better when Dean does.
Castiel finds the boys appreciate coffee, and since he has had nothing better to do, he makes it in the mornings, and Dean will breathe in the steam of his cup, a smile touching the edges of his mouth, and say, "Damn, I slept good."
Castiel's skill as a hunter is not great. But he is very good at this.
So while Dean is in the shower, and Sam is sipping his way through his second cup of coffee, and he mutters to himself, "Since when is Dean a morning person," Castiel feels a glow of pride so intense he actually can't stop himself from smiling, just a little.