Mrs. Grouch is Oscar's mother. She has visited Sesame Street various times over the years, including a 1992 episode and a 1993 episode, usually to make sure that her son is still grouchy and hasn't been turned nice by the other residents. In 1993, she also appeared in the special Sesame Street Stays Up Late, communicating by phone with her son and 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).
According to a talk show appearance on Canadian radio, Oscar's father is from St. David's Ridge, New Brunswick and 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 and Oscar is that whenever Oscar would say "please," she would wash his mouth out with vanilla ice cream.