
Think Helen or Leek from Primeval, Kavanagh, Michael or Wraith from SGA etc, Cylons on BSG, Sarah Corvus from Bionic Woman, The Master or any Dr Who foil, Goa'uld, Ori or Replicators from SG-1, Death Eaters from Harry Potter...the list goes on.
Of course I may be oblivious and there's already something like this going on somewhere out there...But if not, what do people think of it?