She is the daughter of Hugh Test and Lila Test, and her three brothers are Lumpy, Roo, and Johnny Test. Her sister is Susan Test, and her secret name was Mary Lou.
Her aunts are Marie, Angel, Young Nala, Giselle, and Snow White. And her uncles are Proteus and Tulio.
Mary has curly red hair and jade green eyes. She was seen wearing a white jacket, a yellow shirt, glasses, navy blue pants, a light blue moon shaped barrette, and green and white sneakers.
When Mary goes swimming, she wears a pink two-piece bikini with white lining.
Her alternate swimwear contists of a pink and bright orange two-piece swimsuit.
Her other alternate swimwear was a pink two-piece swimsuit with a white moon in it.
At bedtime, Mary wears golden-yellow pajamas with light blue moons and pink slippers.
Her alternate sleepwear is a pair of blue pajamas with yellow moons in it and light green slippers.
She also has her other alternate sleepwear which contists of a white undershirt with a yellow yellow moon in it and teal blue shorts.
As a princess, she wears a royal orangish yellow ball gown with matching shoes, silk gloves, and bloomers, along with a gold tiara and necklace.
When Mary goes to the luau, she wears a light blue bandeau top, a green grass skirt, and a bright yellow lei.
- Mary's full name is "Mary Vanessa Test".