I always figured the warm, fleshy undulating cavities and orifices, and copious amounts of fluids, were part of the vore appeal -- like some odd adjacency to oral sex. Or like "hey it feels good to stick my penis in this hole, I bet it would feel even better if my whole body was in there." (Or "it feels good to eat, and it feels good to have my partner in my orifices; I bet it would feel even better if I put MORE of my partner in there!")
also arrrrrgh darn it Lugia is one of my favorite Pokemon and you got me, Frank Wessssssst XP
.... But also, speaking of Lugia, was it some kind of anthro Lugia the Ditto was morphed into? Lugia's like a seal-whale-dragon creature. Your average Lugia is WAY bigger than 8'8", and also doesn't... really have a distinct "ass" exactly, any more than a chicken does. People and their fetishes are weird. x3;