Mary is a beautiful, smart, athletic, outgoing, perfect mouse who makes Peppa look bad in comparison. Mary Mouse gets the top grades even though she is only in playgroup, and she has won all pageants in the Peppaverse. Every day at school she brings an orange for Madame Gazelle. She is friends with Peppa, Suzy and Danny. She is also very rich and nearly as rich as Emily Elephant but doesn't like to brag and instead donates all of her money to charity.
Her house is a ten-story mansion on a hill with a river of pure water running through it.
Mary has black hair and a rainbow-colored shirt. Like many other characters, she wears black shoes.
Her first appearance was in the episode "Mary Mouse."