Supernatural - Castiel/author choice - Sam and Dean run into a demon who reverses aging, and suddenly Sam, Dean or both find themselves regressed in age (you choose the ages) with only a nervous (I don't do kids) Cas to care for them
Supernatural - Dean/Cas or Sam/Cas/Dean - Evil Castiel - Castiel falls under a spell that makes him evil. Its up to Sam and Dean to save the day. Bonus if love is the spell breaker.
Supernatural - Dean/Cas or Sam/Cas/Dean - Evil Castiel - Castiel falls under a spell that makes him evil. Its up to Sam and Dean to save the day. Bonus if love is the spell breaker.