Robert Foxworth's android acting was great
I loved watching him portray Questor, he really had some great robot-like methods worked out for his role and I wonder if actors who portrayed characters such as Data and Isaac from later TV shows drew inspiration from what he did.
Leonard Nimoy was originally going to play Questor but there's a whole story about why he was pushed out. I can't imagine Nimoy being in that role as I don't think he would have been as articulate in his android-ish mannerisms as Foxworth was.
Credit to Foxworth for establishing such a great character, shame it didn't go anywhere.