Derek as Khal Drogo (but set in snow beyond the wall) and Stiles as Daenerys Stormborn (although he's a greenseer of the Children rather than a dragon)

Derek comes back to Beacon Hills for a number of reasons. The most important one, though, is the result of a one night stand in Vegas. He's knocked up and Alpha, and Cora won't stop playing Papa Don't Preach whenever she gets to pick the music in the car. This shit just keeps happening to him. Or, in which Derek gets the D, Stiles gets the D, then Derek gets Stiles's D.