Mrs. Grouch is Oscar the Grouch's mother. She is also the mother of Oscar's brothers, Ernest & Otto & Oscar's sister Bunny. She has visited Sesame Street various times over the years, including episode 3023 to make sure that her son is still grouchy & hasn't been turned nice. That same year, she also appeared in the special Sesame Street Stays Up Late, communicating by phone with her son & other relatives. In her most recent visit to Sesame Street, she was performed by Leslie Carrara-Rudolph.
Mrs. Grouch lives in Illinois. Oscar remembers her gift of a tattered sneaker to him as a baby fondly enough to sing about it in his signature song, "I Love Trash". Her name is mentioned in Sesame Street Magazine issue 249 (November 1995). Whether she is a widow or divorced from Oscar's father is unknown.
According to a talk show appearance on Canadian radio, Oscar's father is from St. David's Ridge, New Brunswick & his mother grew up in Nova Scotia. St. David's is near Moores Mills, New Brunswick, a community also mentioned in the appearance. That is a reference to Caroll Spinney's real-life parents.
A running gag between Mrs. Grouch & Oscar is that whenever Oscar would say "please", she would wash his mouth out with vanilla ice cream.