The first night Cas spends in the bunker after becoming human, the boys give him his own room. It has everything he needs: a nice bed, a small TV, a bookshelf. Dean had picked out everything in the room weeks prior, before he even knew Castiel's whereabouts. Dean had set up the room for the angel, hoping that he'd come to live with them at some point. Sam had remained silent about Dean's obsessive behavior regarding Cas' room. Dean had been incredibly meticulous about the room, making sure everything was just as he wanted.
Castiel slipped beneath the blue covers on his bed. It seemed that most of the things in his room were blue; in fact, they were the same shade of blue as his eyes. He smiled, able to recognize the intense care Dean put into the room.
"Can't sleep with the lights on, buddy," Dean said with a laugh as he passed by Cas' room, stepping into the doorway. He grinned at Cas who was snuggled up underneath the covers.
"Thank you for the room, Dean," Cas whispered as Dean flicked out the lights, immersing the room in darkness.
"No problem. I'm right down the hall if you need me. Goodnight, Cas." Cas could hear the smile in Dean's voice but the fact that he couldn't see it because of the utter darkness scared him.
All the lights were out and the bunker was quiet and he was scared. He'd been up in his bed, staring at the ceiling, unable to fall asleep. He knew he was safe, but he was still scared.
Cas decided to take a walk, slipping out of his warm bed and shivering as his feet touched the ground. He began to walk quietly down the hallway, tiptoeing past Sam's room, the door standing ajar. He peeked in as he walked by, smiling as he saw the man sleeping peacefully on a bed that finally fit his height.
"Cas?" Castiel nearly jumped out of his skin when he heard Dean's voice. He looked to his right to find Dean peering out of his room, the light still on. "What are you doing up?"
"I...I'm scared, Dean," Cas admitted quietly, feeling his cheeks heat with embarrassment as he looked down at the floor. He didn't see Dean approach him and he gasped a bit when he felt Dean's hand slip into his own.
"C'mon, Cas. You can spend the night with me." Dean's smile was warm as he led Cas into his room. "I'll protect you from the monsters under the bed," he added with a laugh.
Cas spent the night in Dean's bed. And the next night, and the next. And every night.