To achieve the slightly skewed color scheme of the movie, the actors were made up in white face and the color palette corrected until they were flesh-toned.
The Octopus are conjoined twins joined at the leg, but the actresses who played them are not. A prosthetic third leg was designed and fitted to the actresses, but they could not walk while wearing it. This is why the Octopus sisters do not walk in any shot of their whole body.
In the DVD commentary, Ron Perlman said out of everything he'd done in his acting career, the scene where his character attacks Miette under the influence of the Octopus sisters was what he hated most.