Mirroring its super-gross subject matter, each chapter of the Human Centipede franchise has been straight up the last one's ass, taking what was processed in the prior film and shitting it out again, even grosser, for our unwilling consumption.
In the second so-called "sequence," Human Centipede: First Sequence was acknowledged as the piece of nauseating fiction it is, and it served as an in-film inspiration for someone else to create their own, real-life GI tract railroad. And now, in the third and supposedly "final sequence," both previous films serve as inspiration for what is clearly the longest human centipede yet--and in an even more meta turn, director Tom Six shows up, as himself, to smugly grin and give his authoritative advice on the fairly straightforward assembly.
This time, the setting is an American prison, where the warden--played by the star of the first film, even if that doesn't quite make sense--is clearly pretty loosey-goosey with the amendment banning cruel and unusual punishment. His out-of-control inmates are routinely subjected to his "medieval torture methods" that would seem insane were the idea of a human centipede not right there in the title. When this guy waterboards a prisoner, it's with boiling water.
But with those measures still somehow failing to keep the inmates in line, the warden turns to his cohort--the star of Human Centipede 2, because whatever--for counsel on the matter. His response? "Well, have you seen these super-gross movies...?"
Human Centipede 3 (Final Sequence) also features Eric Roberts as the governor, "Tiny" Lister as the prisoner bestowed the honor of being the head of this awful chain gang, and a medical doctor that is basically the "nothing in the rulebook says a dog can't play basketball" judge of an Air Bud film, but for ass-to-mouth surgery. Here's the trailer: