Deliberate mistake: In the lab, when Eddie is riding his motorcycle on the upper level in the wideshots, the stunt double is rather obvious despite the added padding, due to his slimmer face and non-chunky arms.
Deliberate mistake: In order to create the effect where Brad, Janet and Dr. Scott's bodies are turned into stone by Frank, casts were made of the actor's bodies, to create statues of them for the scene. The device turns their bodies into stone, but somehow a pedestal appears beneath both Brad and Janet - although this is obviously to make the statutes stand, where would the pedestals actually appear from in the story? Richard O'Brien, the screenwriter and writer of the original musical, referenced to the pedestals during the DVD commentary, expressing his dislike for them, but also questioning where they would have appeared from.
Answer: It has never been expressly stated, though many theories exist, the primary one being that Frank and the others were sent to Earth simply to experiment on human life and possibly reproduce it (Frank is a scientist, they have a lab, he creates Rocky etc.) and to test their technology on humans. This would require a level of covertness, which Frank disregards by flaunting his hedonistic lifestyle, and thus could have been seen as a failure.
Purple_Girl