The Human Centipede/WMG

This movie is one big metaphor for the perils of capitalism.
The guy in front represents the upper classes, who get all the food/money and who then excrete it down to the lower classes (the act of excretion represents trickle-down economics). The one in the middle is the middle class, who have to take it from the rich and then excrete what they can to the lower classes. The lower class is left dead of blood poisoning, representing the plight of the poor who would starve to death under the pure capitalist system. Heider represents the capitalist government who sets up the whole situation, with the "SWALLOW IT BITCH" scene obviously alluding to Glenn Beck, who tells his viewers every day to "swallow" what the rich give them. The death of Katsudo represents the fact that the middle class can't depend on the rich to keep trickling down wealth to them. Lindsay's situation at the end represents the eternal suffering of the middle class after everyone else is no longer able to help them.
 * Bonus points for Katsuro being Japanese.

This movie is one big metaphor for the perils of communism.
The guy in front represents the producer, who walks, talks and thinks but is burdened by the other two. The others try to suck nutrition from the producer, trying to forget that they're full of shit. Eventually, the producer gives up trying to help those behind him. All die.

Heiter got his idea by playing Silent Hill
Because frankly, the very idea of the centipede is something that could have crawled out of there.
 * Plausible, considering one of the bosses of Homecoming was a human centipede thing.

Heiter was a Tzimisce Ghoul.
Explains why he was so completely Ax Crazy and why he was so obssessed with biology. His master probably does the whole human centipede thing to a far more professional standard. Also explains why he has a torture cellar and a steady supply of rehypnol.

The movie is actually an idea being developed for a low budget horror film.
The entire "movie" takes place in the mind of bored screenwriter who has been unable to sell his "rom coms" and decides make a micro budget horror feature.
 * This explains the ridiculous premise...the lack of basic biology knowledge...and that the passage of time in the film was completely inadequate for the actions described and shown.

The idea came from reading Junji Ito

 * It sure as hell sounds like the plot to one of his mangas.

Guesses to Part 3's Tagline
Each movie so far has meaning behind its tagline:

100% Medically Accurate: Tom Six had to research and ask medical doctors on the possibility of an actual Human Centipede.

100% Medically Inaccurate: Part 2's Martin Lomax had no medical training in creating his own Human Centipede, unlike Part 1's Dr. Josef Heiter.

Doctor Heiter is Mantrid.

 * Specifically, he's Mantrid reincarnated on Earth after the destruction of Fire and Water. Thank christ Stan and Xev never ran into him, you just know it would've been one of those times where Kai wasn't around to help...

The third movie will have fourty-eight people sewn together.

 * The first one had three and the second had twelve, so my multiplication, the third will have fourty-eight. Unless it's done by addition, in which case the movie will have twenty-one.
 * Jossed -- the number of people that make up the final centipede will be 500+!