Col. Zachary Smith, M.D.
Dr. Zachary Smith is a bit of an enigma. Not much is known of his past and that which is known is suspect, as he's an accomplished liar. Reluctant Stowaway establishes Smith as a physician and robotics expert, Welcome Stranger reinforces the fact that Smith has degrees in medicine, but Kidnapped in Space refutes that by suggesting his title of Doctor is honorary. This is just one of many contradictions in the show, which is a continuity nightmare for those of us who care about such things. (work in progress)