Em, sir, a most interesting question.
There's one thing that bothers me, though. Was there a guy behind the set, with long hair and a romanesque chin? Jealously guarding that woman from other suitors? He may have been humming the odd pop tune.
Probably not...it first aired October 27th, 1974...a mere 22 days after Dennis & Karen's first meeting, and a mere 4 days after their first date (according to the Gaines book). GREAT episode, BTW!!