The Munsters (1964)

S1E4 Rock-a-Bye Munster

Herman and Grandpa mistakenly believe that Lily is expecting a baby after eavesdropping on a conversation between her and Marilyn. In reality, the discussion revolves around Dr. Dudley’s son, Elmer, who is set to stay with the Munster family while his parents enjoy a vacation. The misunderstanding leads to a series of comedic situations as Herman and Grandpa prepare for a new addition to the family, unaware of the true reason for Elmer's visit.