According to IMDB the writers wanted Bob Newhart for the part and wrote the role with him in mind. So he did have the makings of a lead, if not a very romantic one.,
I was always struck by the losers Mary dated. They were either whiny dweebs or creeps who looked they’d just walked off the set of a cheap porn flick.
(re: NBC’s Thursday night lineup)
Damn, my childhood really was boring. My Thursday night on NBC was The Huntley-Brinkley Report, Outlaws (a western, generic enough that I don’t remember it), Dr. Kildare, Hazel, and Sing Along with Mitch.