Castiel

Castiel is an angel of the Lord. He became attached to two supernatural hunters. He especially liked Sam Winchester, as he was genuinely grateful and willing to help if needed, rather than being rude like his brother, Dean Winchester.

One time, when the angel was very weak physically and mentally, he came to the Winchester brothers.

"Can I spend the night with you?" he asked then in a hoarse voice.

Dean immediately started complaining—after all, angels don't need to sleep, and waking them up at one in the morning wasn't necessary. But Sam was more perceptive. He let the angel in, made his bed, offered him hot tea, and wished him sweet dreams. Yes, Castiel much preferred Sam over Dean, no matter how good he was. Sam symbolized

In the dead of night, the angel cried out. He had a nightmare about the other angels being angry with him and sending him to hell. The brothers quickly came running to Cas's cry.

“Sorry.. N-nightmare..” the angel said quietly.

Dean burst into swearing. Sam smiled knowingly. Dean told him to go back to sleep and went off to his room, dissatisfied.