In Tom Six's torture-porn game-changer The Human Centipede, an evil German doctor (Dieter Laser) kidnaps a Japanese man and two vapid American girl tourists, imprisons them in his basement lab and shows them a presentation of simplistic hand-drawn slides that illustrate his diabolical plan: By surgically connecting all three via digestive tract, he will turn three beings into one. Just like that, an iconic movie monster is born.
The notion of a human centipede assumes that live bodies are interchangeable widgets, and thus as long as there are more available, the centipede can keep growing indefinitely, and it'll be exactly the same, except more horrible. The sequel possibilities are endless. But even with a confirmed follow-up on the way, the film also mocks the idea of a traditional horror franchise, where the monster/threat/body count gets bigger with each iteration. (This Godzilla movie is just like the last Godzilla movie, except now he's even more radioactive! Human Millipede is just like Human Centipede, except with even more gastric extension!) Either way, Six has created a marketer's dream — if not for the whole “ass to mouth” thing.
Yes, The Human Centipede depicts three live humans surgically attached so that food fed to one has to pass through the other two, but the film itself is not as scat-pornographic as you might think; there's no excrement on-screen. (That said, when spoken in Centipede, the line “Swallow it, bitch!” gruesomely transcends its usual hard-core-porn context.) Never as explicit as a Saw or Hostel film, Centipede disarms the viewer with comedy early on (the doctor is so demented and the Americans so stupid that at first, Centipede plays as parody), then swiftly shifts into the shit (literally and figuratively), managing to maintain a steady aura of stomach-churning dread purely through performance and suggestion. It's definitive psychological horror, positioning the viewer to identify with the victims' suffering and lack of free will, even after harshly judging what they did with that free will when they had it.
In fact, The Human Centipede is startlingly relatable: Six uses the centipede to talk about being human. In the tradition of the first Frankenstein films, various contemporary “enhanced interrogation techniques” and certain interpretations of Catholic purgatory, Centipede plays on the notion that the only thing more frightening than death is a state bridging life and death, in which, though one's body is no longer his or her own to control, the mind remains conscious. In Six's view, the moral imperative to preserve life only goes so far — eventually, death is a relief.
Centipede may fit into a certain horror tradition by hyperintensely depicting the fundamental fear of limbo, but it zigs where most of those films zag. If the standard cinematic way of dealing with that fear is by giving victims a last-minute burst of heroism to arrange their own reprieve, then The Human Centipede is truly subversive in its hopelessness, its refusal to transform its victims into self-saviors with dubious impromptu powers. Centipede ultimately manages to correct mainstream horror's bullshit conservative ideology. It's become an old film-theory chestnut that the horror heroine who says no to sex gets to live while her friends die — thus, the Final Girl. There's no sex at all in Six's beyond-twisted vision, but in the end, the final girl is well and truly fucked.