Michael Francis “Bub” O’Casey, was a feisty old coot of a housekeeper and father-in-law of engineer Steve Douglas (Fred MacMurray) on the sitcom MY THREE SONS/ABC/CBS/1960-72.
Bub earned his moniker because the young Douglas kids couldn’t say “Grandpa” hence their attempt in speaking his name turned into “Bub.”
Note: When William Frawley left the series midway through the 1964-65 season for health reasons, he was written out of the script (by traveling to Ireland) and replaced by a similarly crusty old relative named Uncle Charlie O’Casey (William Demarest), a retired sailor.
Shortly after leaving the show, William Frawley died of a sudden heart attack on March 3, 1966. Frawley was famous for his role as the tightwad of a landlord and best friend of the Ricardos on the 1950s sitcom I LOVE LUCY.