Grammy Moon is a character on the sitcom Frasier. She is the mother of Harry Moon, and the paternal grandmother of Daphne Moon. She is often the topic of conversation by Daphne, much to the rest of the household's distaste. Daphne speaks of her in many long-winded stories, usually about peculiar health tips or cooking recipes. She is never seen or heard on the show, but mentioned many, many times. This last trait makes her similar to Maris Crane, she is confirmed to have died in season 3 when Daphne says everyone had to go to her funeral.
It is worth noting that "Grammy" is not a word English people generally use to refer to their grandparents. It is American in origin. Whether the writers knew this or not remains to be seen.