In the explanation of who Betty Jo Elliott is to Jed, Granny tells him he's Kate Bradley's daughter. That she needs to go to Hooterville because Cousin Pearl hurt her back dancing. These are references to both characters played by Bea Benaderet in the HenningVerse. This episode aired 18 days after Bea passed away.
Jed says they're "leaving for Petticoat Junction." This is an overt plug for the sister series, as the term was never used in the show itself; it was always just "Hooterville."
Drysdale mentions that Miss Hathaway has worked for him for 11 years, confirming that she was with him for four years before the Clampetts arrived.
When Jethro is going to get the directions to the city Hooteville, from Uncle Joe, he sits down at the kitchen table with pen and paper. As he starts to write he chews the pointed end off of the pencil. When starts to get the part of pencil he chewed off he starts to write. The lead never touches the paper as he writes and also the point goes off the paper and onto the table. He continues to write
The reason given that Pearl can't take care of the baby is given that she sprained her back dancing with Walter McKeegan. This is another instance of a staff member's name being used as a character name. McKeegan is the art director on all three shows in the 'HenningVerse' , Beverly Hillbillies, Green Acres, Petticoat Junction.