Cathy did not appear in this episode.
Interestingly, this episode (in which Patty Lane realizes that she is too young to marry Richard) was directed by Harry Falk, who at the time was married to then 19-year-old Patty Duke.
This is the third of three credited appearances Ronnie Schell makes in the series, each time playing a different character. His other appearances occur in Our Daughter the Artist (1965) and Patty, the Candy Striper (1965). At the time of his appearances in this series, he was already playing a recurring role as Duke Slater in Gomer Pyle: USMC (1964).
Judy Carne would follow her one appearance in this series by starring in her own TV sitcom: Love on a Rooftop (1966), which put her in a similar role as a young newlywed trying to navigate the trials and tribulations of marriage. She, of course,, is perhaps best remembered as a regular cast member on Rowan & Martin's Laugh-In (1967).