Catherine Frensky

Catherine Frensky is Francine's high school-age sister. It was said that Catherine is in Grade 10 in the episode Vomitrocious. She was originally voiced by Patricia Rodriguez who also originally did the voice of Sue Ellen, and is currently voiced by Alexina Cowan. The name of the high school she goes to is unknown and has never been seen, although she was revealed to have some high school friends in some segments. In the episode "The Frensky Family Fiasco" it is revealed that she is a vegetarian.

Appearance
Catherine is described as brown monkey with long red hair and bangs, with her long hair tied into a ponytail. She usually wears a blue shirt jacket, yellow shirt, and blue pants. She made her debut in the segment Francine Frensky, Superstar, and has appeared in subsequent segments as well.

Personality
Catherine is probably the exact opposite of Francine. She is described as girly and very responsible. She enjoys reading teen magazines and frequently uses the telephone. Like sisters Francine and Catherine go thorough various fights like how to decorate their room in Francine Redecorates and who gets the last soda. She briefly wore lipstick in one scene of My Dad, the Garbage Man, and nail polish in one scene of Stolen Bike, but usually prefers to keep it natural. But Catherine can help her sister see what's wrong like in episode Citizen Frensky when she took pictures of her to make her feel what it's like to be made fun of. She also tried to help Francine after she learned that Francine unknowingly plagiarized an entire paper for her Thanksgiving report in Francine's Pilfered Paper. Francine and Muffy had attempted to pair her and Chip together in Matchmaker, Matchbreaker, but Chip and Catherine are only friends. They told Francine and Muffy that they have no romantic interest in each other. In Francine Frensky, Olympic Rider, she and Francine took riding lessons together to which she turns out to be a better rider at first than Francine. She also developed a crush on Stanley, an instructor at the Aegean Stables. Also, there were times of when she used to babysit Arthur, D.W., and Kate while their parents were going out in Play it Again, D.W. and D.W.'s Name Game.

Friends
In Muffy Gets Mature, some of her friends from high school are revealed, including Angie, Tammy, and Debbie. However, her friends have rarely appeared again, since.