I never knew, till learning just recently, that actress Marie Blake, who portrayed Grandma Addams in this series, was the older sister of singing '30s and '40s major screen star Jeanette MacDonald.

Marie's original name was Edith Marie Blossom MacDonald. Blossom Rock was the name that Marie, in her personal life, was most known by, as Blossom was the name she had gone by since I believe childhood, and Rock was her marriage last name. Therefore, by the time of The Addams Family, Blossom Rock was the name (and it was her real-life name) she chose to be credited as. Meanwhile, Marie Blake had been her professional name throughout the majority of her acting career, which is why that's the name she's primarily listed under on TMDb and IMDb.

At any rate, I never would have guessed that Marie/Blossom was Jeanette MacDonald's sister, as there was no real resemblance, and the two women were entirely different types. Plus the names situation, of Marie/Blossom never having professionally gone by the last name MacDonald, further throws one off the scent.

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