This is a short fanfic but i thought this was a cute idea and I can just see this happening :p
Dean yawned as he came into the bunker, he was up all night and finally just got back from the hunt, Sam wasn't really tired since he got to sleep on the way back and Cas didn't need sleep. Dean sluggishly headed right to his room for a needed nap, Cas followed him from behind.
"Yes, Cas?" Dean said, hearing Cas's loud footsteps.
"Where are you going, Dean?" Cas asked.
"To take a nap..I can't pull another all nighter like this" Dean responded.
"May i join you? I know i can't sleep but-" Dean grabbed Cas's hand.
"Yes you can join me" Dean and Cas both smiled at each other. The two headed to his room, Dean was about to pass out as they finally got inside. Cas closed the door behind them as Dean laid on his bed. Dean wrapped an arm around Cas as he laid next to him.
"Night Cas.." He immediately fell asleep, Cas looked at the man holding him in his arms, though he didn't need to sleep, he didn't mind the beautiful view. He could stare at him all day, Cas wrapped his arms around Dean's waist as he slept.
Even though Dean's eyes were closed, Cas could just imagine those beautiful greens eyes staring at him. He couldn't help but smile as he was laying against the man he loved. Cas looked up at Dean's face, he started to brush his finger against Dean's jawline.
"Why do you have to be so adorable?" Cas asked a loud to himself, he began to listen to Dean's heartbeat. The calming beat it made forced Cas to blush. The beat started to speed up a bit, causing Cas to look up at Dean's face. Cas noticed Dean had a look of fear on his face, maybe he was having a nightmare?
"Cas..Sammy.." He said quietly in his sleep, Cas sat up a bit. "Don't..please.."
"Dean?" Cas said quietly, not trying to wake him.
"Help..please.." Cas smile turned into a look of sadness, he set a hand on Dean's forehead and closed his eyes. Dean's quiet calls for help became quietness, a small smile appeared on his face.
"You deserve sweet dreams, Dean." Cas laid down next to him again.
"I love you, Cas.." Dean said in his sleep.
"I love you too, Dean"