I got curious and googled her a bit. It seems she's one of the tallest characters, "rivaling Waluigi's height". I guess "tall" memetically morphed to "big".
Well, considering the Square-Cube Law, volume (and consequently, weight for denser material) increases more drastically the taller you get than one might expect. I imagine the only reason Waluigi is a middle-weight compared to Rosalina is because of his stick figure, compared to Rosalina who has more curvature to her. She'd probably just barely fit into heavyweight-class karts, then, in my opinion, as opposed to characters like Bowser and Donkey Kong, who'd be heavyweight without question.
So, it's not because she's fat or anything, she's just a tall, curvy lady.
I got curious and googled her a bit. It seems she's one of the tallest characters, "rivaling Waluigi's height". I guess "tall" memetically morphed to "big".
maybe it is because mario kart 8, i still dont have it but it could be that she has the same weight as bowser there
When she first appeared in Mario Kart Wii she was classified as large-class. In Mario Kart 7, she was a cruiser-class along with Donkey Kong and Wiggler. In both of those cases, it was clearly because of her height; however Mario Kart 8 does away with cruiser-class, so she had to be re-classed as a heavyweight.
As a side note: She is not the first heavyweight female, that goes to Honey Queen in Mario Kart 7.
If we're going by Smash and Mario logic, she's heavy because she's used to the weight in space which has a much lighter gravity. The gravity of Mario World is heavier so it effects Rosalina harder because she's normal weight on the lighter gravity of space.
I heard that, at the beginning of "Super Mario Galaxy" development, she was as tall as Princess Peach. But Konno Hideki, the producer of Mario Cart series, proposed the redesign to treat her as the first heavyweight-class female driver.
The same as Bowser!!Heavyweight class!!Heavyweight class!!Weight scale!The first female!Rosetta-san is cute!! Cute! Cute!Who weighs more? Donkey Kong?