All over lj like a rash at the moment. I tried to apply this to HL, too, but it didn't work there for a load of reasons - mainly because HL is far more sane and rational than the murky, swirling deeps of HP.
I,
rochefort, do solemnly swear that my favourite HP character is Remus Lupin and my equal-least favourite characters are Dobby and Kreacher, the house-elves. The mere thought of them doing naughty things together makes me whimper. However... given sufficient crack and an infinite number of monkeys, here's how a Lupin/Dobby and/or Kreacher shag might happen (though I sincerely hope it never does, and if it does, I just don't want to know).
Necessary plot device or deus ex machina: Shut up in his room at Grimmauld Place and under the influence of wolfsbane, Remus transforms at the full moon. As Kreacher has never returned after he set up Sirius and they need an elf around the house, Harry has brought Dobby along to do the housework. Ever-considerate, Dobby realises that in his werewolf state, Remus will be without his socks and decides to take him two pairs to keep his paws warm.
Who makes the first move: Dobby, overcome with lust at the sight of a magical creature whose coat means he doesn’t need socks, starts licking Remus’s furry feet.
Positions and/or kinks: It’s HP fandom: bestiality’s a given. And it soon becomes a threesome when Kreacher returns unexpectedly to retrieve some of the Black family’s dark-arts books. From there it degenerates into bondage-fic (using socks) and hot elf-on-elf action while the werewolf watches.
Afterglow: Remus gets carried away with excitement at his first shag since Sirius died, and bites off Dobby and Kreacher’s elfhoods, thereby dooming them to live wretched half-lives as were-elf castrati. When he transforms back the next day, he decides this is a fitting punishment and sneaks the elves out under cover of darkness, apparating with them to the Forbidden Forest. There he sets them free, with a promise that if he ever sees either of their sorry arses again, he’ll AK them on the spot.
Would I actually read or write this? One of the funniest HP fics I ever read was Harry/Dobby. So maybe someone could do it. But this outline is as far as I'll ever go towards dipping my toe into this particular little foetid pool.