Lisa Loring played the Addams' daughter in the original 60s series at the age of 5 1/2 (memorizing lines before she could read) and then appeared with most of the original cast in the 1977 made-for "Halloween With the New Addams Family"--after the original show ended its run, she went on to the Phyllis Diller bomb "The Pruitts of Southampton" (which was renamed mid-run "The Phyllis Diller Show"--didn't help) and had a good run playing Cricket Montgomery on "As the World Turns"--of a stroke in Burbank with her daughters at her bedside:
Correcting the THR obit, MGM, which owns the Addams IP today (including the Netflix hit "Wednesday"), did not produce the original series--it was a Filmways presentation, dahlinks (bought by Orion Pictures in 1981, which was acquired by MGM in the late 90s).