Joan Marshall (Phoebe Munster) was replaced by Yvonne De Carlo (Lily Munster) for the series, as Phoebe was thought to be too much like The Addams Family (1964)'s Morticia Addams.
Working title: 'Love Thy Munster'.
While Grandpa is mixing his potion, he names the ingredients as he adds each one. One them is "GL70", which he squeezes out of a tube that resembles toothpaste. Indeed, "GL70" is the "secret" ingredient in GLEEM toothpaste, a popular dentifrice of the day.
After the close-up on the recipe book in the basement, the scene where Grampa makes a potion continues in one uninterrupted take of more than two and a half minutes, unusual for sitcoms.