Arthur/Merlin temporary girl!Arthur Arthur gets turned into a woman while he and Merlin are away from Camelot, and Merlin can't immediately turn him back. He and Merlin have to pose as husband and wife, for some good reason. They weren't sleeping together before, though pining is fine (pining is a wonderful idea). Now though, they have to share a room and a bed... I'd love to see Merlin being the actively protective one for a change. (He's always protecting Arthur, but behind the scenes - now he gets to step forward and tell people off for leering at his wife. :-D)

Girl!Arthur (done amazingly well)