This is Wendell Holmes's last of five appearances in the series, the second as Mr. Blair. He died at 47, on April 27, 1962, three months after this episode first aired.
The apparent love/hate relationship between Beaver and Penny has precedent from season 3 in Beaver's Team (1960), where Penny and Beaver at first enjoy a bond that is at least amicable. Penny even shows signs of infatuation before Beaver ultimately insults her.
This is the last time Jean Vander Pyl appears in the series. In all, she makes five appearances, this time and once before as Penny Woods' mother. She is perhaps best known for lending her voice to the role of Wilma Flintstone, in the animated series The Flintstones (1960).
Penny Woods' father's name, Henry, is revealed on the party invitation wherein Penny's mother signs herself as 'Mrs. Henry Woods.'
Because Penny does not move away from Mayfield with her parents, this is not the last time Karen Sue Trent appears in the series. She plays Penny Woods once more, in the next episode: Beaver, the Bunny (1962). In all, she appears in 14 episodes. The first, from season 3, simply lists her in the credits as "Cowgirl."