Patrick Bauchau arranged for the filmmakers to use the medical set of his television series, The Pretender (1996)
Blake and Francis' look was inspired by old photographs of Chang and Eng Bunker.
The film does not take place in a town called "Twin Falls, Idaho". Rather, the film's title refers to the fact that Blake and Francis are "twins", their surname is "Falls", and they're living in a hotel on "Idaho Avenue".
To keep the focus on the human element, the Polish brothers wanted to give the film a timeless quality hearkening back to the 1970s, '60s and even '30s, when Chang and Eng Bunker were still alive who were the inspiration for the film. In 1972, for instance, the year Blake and Francis were born, medical science did not have the equipment or know-how to separate twins fused so intricately. Instead, conjoined children were most likely hidden away from the world by stunned parents, or given up for adoption. For Blake and Francis' mother, "time stood still when her sons were born," explains Michael Polish, "and in some ways the twins, too, remain stuck." As a result, the twins' clothing is reminiscent of an earlier era while their mother's apartment-number 1972, significantly-is decorated in the bright orange hues that were popular three decades ago.