When some asshole hits a dog with his car and drives off, the first two people on the scene are Dean and Castiel. Castiel's an FBI agent with a plane to catch, and he doesn't have time to take the dog to the vet. Dean's a musician, and he doesn't have the money. An agreement is reached: Dean goes, Castiel pays, and they'll exchange details and meet again to work things out. But who gets the dog? Sooner or later they're going to realise that having shared custody of one pitbull isn't ideal. She needs one home, not two. One stable, loving home...
AU. A sailor and an enemy pirate are marooned on an island together, and while awaiting rescue they accidentally achieve domestic bliss.
Or:
Dean Winchester is lieutenant of the Royal Trading Ship Echelon. On a pleasantly sunny but particularly catastrophic day, he is marooned on an island somewhere in the middle of the Pacific Ocean with only one man for company. That man is Castiel, captain of the black-sailed Leviathan: a pirate, no less. Given the circumstances under which they are stranded, rescue seems unlikely, and it could be aeons before a ship even comes by. The two of them may as well make the most of their own private island, personal differences be damned.
As the one-year mark of the Unpocalypse approaches, Aziraphale pointedly mentions to Crowley that he'd like to spend the anniversary doing "something lovely" with "somebody special". Thus, Crowley secretly plans a surprise picnic in Tadfield with Anathema and the Them. Of course, this comes served with a plateful of misunderstandings, a side of moping, and a seasoning of mischief... eventually followed by a deliciously pleasant afternoon.