Minor follow-on from the 'alien design' post. edblog tells me that the job of designing the original Dalek costume was given to a young whipper-snapper called Ridley Scott. You see, what goes around comes around. The dalek design we now know and love was not however Ridley's, as he made a mess of it, and the job was assigned elsewhere.
Could it be that the rejected Dalek design had an alarmingly phallic extrudable jawbone and/or was envisaged as leaping out of the Doctor's chest?