Cas would always watch over Dean while he was sleeping. It didn't matter where the hunter was, or who he was with. Sometimes he would remain invisible, and other times he'd just sit on the edge of a bed, watching, as Dean Winchester slept and dreamed.
"Why do you always watch ME sleep?" Dean demanded one night. "You never go all stalker mode on Sam when he's sleeping."
"I like watching over you." Cas insisted. Dean rolled his eyes, shrugged out of his jacket, and flopped down on his stomach on the cheap motel bed, hoping to get a few hours sleep before he and Sam started their hunt the next morning.
Cas settled himself at the foot of the bed, sitting crossed legged and intently watching the hunter.
"It's creepy." Dean mumbled. "Could you maybe NOT stare at me all night?"
"Maybe I'd stop watching you so closely if you slept in a safer way." The angle offered. Dean rolled over, raising an eyebrow in confusion.
"What do you mean?"
"You always sleep on your stomach, Dean." Cas explained. "And that's very concerning. You could suffocate very easily."
"Cas, I've never suffocated in all the times I've died. I don't think you have to worry about that." Cas frowned.
"Still. I'd feel much better if you slept on your back."
"Not happening." Dean said fiercely, pointedly rolling back onto his stomach. Cas paused, wondering if he had stepped on an unknown nerve.
".....Dean?" The hunter turned on his side, staring at the wall.
"Forget it, Cas."
"But I've made you upset." The innocent angel offered. "And I was told that humans should never go to bed mad at each other."
"I'm not mad." Dean sighed, shaking his head. "It's stupid, Cas. I just like sleeping on my stomach, okay? And if that means you're going to watch me like a hawk, then fine. Whatever. Goodnight, Cas."
The room fell silent for a minute before Cas decided to ask.
"Dean?"
"What, Cas?"
".....Why don't you like sleeping on your back?" Dean clenched his eyes shut.
"Don't worry about it."
"Please tell me. Maybe I could help!"
"You can't help my weird irrational fears, okay Cas? Just let it go."
"I'll let it go when you give me a proper reason." Dean sat up, a complicated look on his face that Cas had never seen before.
"You really want to know?" The hunter snapped slightly.
"Yes." Cas said sincerely, gazing at him. Dean shook his head.
"It's just...." He bit his lip. "I'm always afraid that if I sleep on my back, then, when I open my eyes, I'll....."
"You'll what?"
".....I'm afraid I'll see someone I love on the ceiling." Dean admitted, looking Cas in the eyes. The angel stopped, not quite sure what to do.
"Well...." He began. "I'm always watching over you at night, Dean."
"I know." Cas took the hunter's hands in his.
"And I promise you, Dean. As long as I'm watching you; no one will end up on the ceiling."
"But what if you're the one who ends up burning up there?" Dean asked. Cas smiled.
"I'm an angel of the Lord, Dean. It'd take a lot more then a ceiling fire to keep me from you."