while the doctor's other old enemies the daleks did not change during the original series's twenty-six season run, the cybermen were seen to change with almost every appearance. the cybermen are humanoid, but have replaced their limbs and other body parts with non-living parts to the point where they don't have many flesh parts. in their first appearance in the series, the only portions of their bodies that still seemed human were their hands, but by their next appearance in "the moonbase" (1967), their bodies were entirely covered up in their metal suits, with their hands replaced by two finger claws, but changed back to regular five finger hands in "the invasion" (1968). as there are not many of them, the cybermen often convert humans to cybermen.