A quick overview of these movies.
Dieter Laser as the mental unbalanced Dr. Heiter.
The Human Centipede is, according to its IMDB page, about "a mad scientist [who] kidnaps and mutilates a trio of tourists in order to reassemble them into a new 'pet'-- a human centipede, created by stitching their mouths to each others' rectums." The movie is filled with the terribly acted stereotypical characters (the crazy surgeon, the inarticulate foreigner, the hopelessly dumb young girl) that you usually find in the horror genre. Occasionally, there are a few interesting shot choices and fluid transitions, but mainly it is generically filmed. The worst part of the film, however, is the writing. Expected dialogue and boring plot twists abound.
Snakes on a Plane is not very different, with the exception of the always excellent Samuel L. Jackson filling the main role. Its title also spells out the entire plot of the movie.
Tom Six, director/creator of The Human Centipede, is not credited with making anything else of note, but the director of Snakes on a Plane, David R. Ellis, is the director of such unappealing classics like Cellular and Final Destination 2. Clearly neither have much of a track record, but there is one thing separating them from all of the other run-of-the-mill filmmakers out there: money.
The shocking thing about these two films is that regardless of the mediocre production value, the even more mediocre acting, and the altogether horrible writing, they actually managed to make money. The Human Centipede has made about $2.3 million, while Snakes on a Plane has made over $85 million. These movies have made this money purely on the shock value that their titles and central gimmicks have produced.
As young filmmakers trying to break into the business one way or another, these films provide at least a minimal amount of inspiration. With a fair amount of connections and an original gimmick for a movie, you, too, can earn back enough cash to produce something worth while the next time.
Here is the Patton Oswalt clip, but be warned: it's got some pretty highly offensive language in it. It may not be suitable for everyone.