Speaking of the robot's lower extremities, there's a classical blooper from one of the original series' best episodes, "Invaders from the Fifth Dimension." In a scene where the robot approaches the invaders' space ship, its lower half was to be hidden with boulders and shrubbery, but for one moment one can see, quite clearly, that most of the bottom is gone and the legs of the actor, along with cables, are clearly visible. Unfortunately, no butt can be seen.
Gerard