Dean knew Castiel liked him. It was so obvious. And so where Dean's feelings.

So when Cas and him where hanging out in his bedroom one night, Cas leaned in and kissed him…and Dean kissed him back, just to pull away quickly, realizing he'd just kissed Cas. A man.

“I- I can't..." Dean felt immediate guilt and pure shame for kissing another man. "I wish you where a girl, Cas…”