Commission for Seydaschu of his hyper stretchy (hyper talented?) snake guy taking a huge dick up the ass. It might've started as sex... but it all depends on your point of view. If you ask him, he'd say it's penis-first anal vore.
He also wrote a short story to go with it, which you can read here: http://www.furaffinity.net/view/25541307/
There's a version without the dialogue attached to this post, as well.