Mary was a super genius girl. She was one of Johnny's sisters, and Hugh and Lila's daughter. She was voiced by Ashleigh Ball.
Mary has curly red hair and she has greenish blue eyes. She was seen wearing a light gray jacket, a yellow shirt, navy blue pants, glasses, a light blue moon shaped barrette, and green shoes. Her swimwear was a bright pink bikini. And her disco outfit was a bright purple tank top with silverish gray shoes and bright pink shorts.
- Sleepwear - Bright yellow pajamas with light blue moon symbols.
- Alternate sleepwear - Bright blue pajamas with bright orange moon symbols.
- Western outfit - Bright yellowt shirt, pink bandana, bright blue pants, and brown shoes.
- Early 50s outfit - Light blue t shirt with navy blue moon, light gray bandana, light gray poodle skirt, light gray socks, and usual shoes.