The first one I found to be darkly comic, but more comic than anything else. Mad German doctor decides to kidnap three people at random and turn them into a, you guessed it, human centipede. I'll leave you to imagine how that worked and what depravity was required to get there! But it was comic in The Man With Two Brains type way. So absurd that you just end up laughing at what is going on! The actor playing the doctor is Dieter Laser who executes it deliciously looking the part perfectly!
The second one is probably the best as we follow a fan of the first film trying to take the idea further and make a human centipede with a chain of people, so many more than the three. This one is shot in black and white and very stylish, through the gore and violence, in a David Lynch type way. The mad fan is an under-trodden car park attendant abused by his mother (think Psychoville).
He exercised his power over others by re-enacting the bones of the film he loved so much bumping people off left, right and centre in the process. Leaves very little to the imagination and has to be seen to be believed. The fan is played by Laurence R. Harvey kitted out with wild eyes and does it scarily.
The third one really is utter nonsense and rubbish as Laurence R. Harvey and Dieter Laser are thrown into a situation in an American prison where one is the warden and the other his accountant. Laser is off his trolley again and hatches a plan to make the longest human centipede ever with all the prison inmates. And even has a go at a human caterpillar! Chaos and madness ensue. This really is the weakest of the three films and is all just rubbish!
Tom Six is behind all this mayhem and even appears in the third film as himself as the lines of reality intersperse with filmmaking and fandom moving forward. It's all absolutely chaotic, mad and daft - leaving you wondering why on earth anyone would make such nonsense. Unbelievable - the most bizarre thing I have ever seen.