post dicknecks/neckdicks or whatever you want to call them.
http://bobboled.deviantart.com/ also has a number of stories along these lines, though be warned he's also got a huge anal fetish I mean like seriously TFs everything into asses when he can.
You ever get the idea in /d/ that a fetish you see posted can't possibly be sexually arousing to anyone, and only exists for the exact purpose of being as fucking bizarre as possible to mess with people?
This is one of those times.
If I had to muster up some kind of explanation as to why this gives me a boner, I would guess it's because it's a combination of a detachable head/limbs fetish with a selfcest fetish.
http://legendsofbelial.no-ip.info/ says hi, the place for all sorts of these kinds of transformations and more