Dean has things to think about, Sam and Jackie watch and observe from a distance, and Cas doesn't let anyone touch his trench coat. (No warnings, but more flirting) Part Two of Relationship by the Water
Sam and Jackie are getting married, Dean can't be happier, and Cas is distressed. Part Four of Relationship by the Water
Cas and Dean fight, and it's bad enough where Cas slams the door to the bunker as hard as he can when he leaves. (Seasons 6-8 spoilers, Past Cas/OMC, dub-con) Part Three of Relationship by the Water
Some days are better than others (like when he doesn't feel the need to strangle the two idiots, because he can't). *Small hint of Sterek, but could be read as Gen. Spoilers for season 1.