The vast majority of people with mental retardation have IQ levels of 55 to 69 and are considered mildly retarded. Mildly retarded children often go undiagnosed until they are well into their school years. They are often slower to walk, talk, and feed themselves than most other children.
When Tom Six began creating the Human Centipede sequels, he envisioned a trilogy that works as a movie centipede. Each sequel opens with the ending of the previous film, as the events of that film influence said sequel.
Although The Human Centipede is set in Germany, principal photography took place in the Netherlands due to the neighboring countries' similar landscapes. Heiter's home, where most of The Human Centipede takes place, was a villa in the Netherlands found by the production team.