Mary somewhat resembles her daughter. She is a blue cat just like her, with a slim body and wide hips, but with a rounder face, pointier ears, smaller oval-shaped eyes, longer whiskers, a longer tail, and a different mouth type. She only has five visible whiskers like her grandson Gumball. She is taller than both her husband and her daughter.
She wears a yellow-orange sleeveless turtleneck blouse, a long dark blue skirt with a brown belt having a white buckle, and brown heeled sandals.
In "The Parents," she is shown in the present with a more elderly appearance; her fur is a little paler, her whiskers are grey, and there are wrinkles under her eyes and on and around her mouth.
In "The Choices," Mary, unlike her husband, is presented as very calm but somewhat snobby and strict. She, along with Daniel, seemed to value success over love and was determined for her daughter to become very successful, by constantly placing high expectations in academics and physical activity, making her daughter take every extracurricular activity and telling her that “second place is first place for losers.” Her and Daniel's expectations were so ridiculously high she once even chastised Nicole for having an "F" for “gender” on her report card.
She and Daniel also did not approve of Richard and believed Nicole could have done better. This, the stressful childhood that was brought on by her parents’ constant high demands and expectations, and her desire to start over and not bother trying to fix a broken relationship led Nicole to storm out on her parents in her late teens after an argument.
However, Mary has a softer side as she was saddened by Nicole storming out, suggesting that despite her ambition for Nicole having a successful life, she truly and deeply cares about her.
"The Parents" shows her and Daniel reuniting with Nicole after twenty years thanks to the latter's kids. Mary and Daniel both try to defend their parenting, claiming they wanted what was best for her and for her to succeed and that Nicole's anger issues and resentment towards them did not make things easier. Mary also reveals that she and her husband did try to go to Nicole and Richard's wedding in spite of their disapproval of their relationship but got lost because they mistook RSVP for Rsvp, a town in Moldavia.
She and Daniel seem heartbroken when Nicole comes to the conclusion they were better off separated, and they seemed to have missed Nicole during all that time. She and Daniel end up driving back to Nicole's house and Mary tries to say something, but Nicole cuts her off and says she does not want to hear her excuses, she just wants them back, and the three hug, finally fixing their relationship.
- "The Choices": Mary and Daniel's first physical appearances; she chastises young Nicole about her grades on the car ride to the latter's karate tournament, and then she and Daniel force her to run after the car breaks down. They also are shown participating in Nicole's later teen years, becoming estranged from her after a fight and not showing up at her wedding
- "The List" (photographed in a locket)
- "The Parents": Her and Daniel's first major role. She and Daniel reunite with Nicole and try to talk about their problems with one another, which ultimately leads them to reconcile.
- "The Web": She appears in a photo.
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- Mary and Daniel's names were revealed in "The Parents."
- Nicole may have inherited some of Mary's perfectionist behavior and abnormally high academic expectations, as demonstrated in "The Fridge."
- "Senicourt" is the maiden name of Nicole Bocquelet, Ben Bocquelet's real-life mother.