Grandma Marsu (real name unknown, but in some language or other, it must be something that translates as "unique") is Mars' mother, Mia's inlaw, and the grandmother of Bibi, Bibu, and Bobo. She only made one appearance in the episode "Grandma Marsu" of My Friend Marsupilami. Although, she has been mentioned in Disney's series by her own son (Mars: Mother always says "look, but don't touch"... Of course, I always prefered to touch and not look.), and if the two versions are indeed the same character, then she's long been a single parent that has been stressed out by raising Mars on her own, but over time, she's learned to loosen up and enjoy not only her son but her grandchildren as well... she and Mia have several disagreements, most notibly over the right weaving technique for re-building a nest, which indicates Grandma Marsu is somewhat skeptic over her son's choice of mating, yet she's glad Mia was picked out from the rest of the seperated "tribe" of there species... if only Mia wasn't so stubborn, especially around her.
Obviously, judging by behavior, Grandma Marsu's side of the family that Mars got his sence of humor from, along with his interest in human lifestyles (she easily took her son's side when he wanted to add those things to the nest reconstruction), but the problem is that Grandma Marsu has less control over her laughter then her son does (especially when she's making fun of David Newman's clumbsiness and how he blinded himself with dirt trying to chase away a parrot), and so overstimulates the sence of humor of the rest of her family (most oftenly her son and her grandson, Bibu) until somebody gets hurt bumping their head on the ceiling. It wasn't until that happened to Bibu, and the little guy got too dizzy from the impact to climb trees that she felt guilty, and Grandma Marsu's laughter was replaced by tears of sorrow as she prepared to leave that part of the jungle... but without her, there wouldn't be a nest-warming party, and no nestwarming means the Marsu-family cannot move into there reconstructed nest! It was up to Mars, the only one in the family of Marsupilamis that knew her best, to cheer her up. Mars refused at first, as his mother brought the mishap on herself for disrespecting his human friends' house-rules (No Marsupilamis Allowed in David's office), but Mia's nagging and the crying of his children convinced him to talk to Grandma Marsu.
What he said to cheer her up was undeciferable, but how he said it must've reminded the long-widowed Grandma Marsu of his father, and the way they comfort eachother with a hug shows that no matter how much she embarresses Mars, no matter how grown up he gets, he's still her hatchling, and a part of him will always need her.
After the nest warming, concluded with traditional seed-spitting, and a not-so-traditional honor of making David "first in the nest", Bibu's dizzy-spell wore off and everyone celebrated with an ancient marsupilami chant lead by Grandma Marsu herself. When Mars, Mia, and the triplets had their own nest again, Grandma Marsu kissed the relatives goodbye and, before leaving, gave David her most prized possesion (a hat made of large jungle flowers) as an offering of thanks for him giving her the rare-yet-wonderful gift of laughter. Marsu began to miss his mom once shes gone, and gave David a congratulatory kiss when he saw the man wearing her hat... who knows? Maybe we would see her again.