I talked to Mark Goddard several years ago when he was a guest on the trivia/nostalgia show I listen to on Saturday nights on WBZ out of Boston. By that time he had retired from acting and was a teacher in a Massachusetts public school. Really a pleasant guy, very down to earth.
I asked him about the on screen hostile dynamic between his character and that of Dr Smith (Jonathan Harris) and if there were any blooper reels of their scenes together. He chucked and said there were, but as far as he knew they were not in the public domain, and in any event most of them could not be played on air or in polite company.