Rosalina developed a case of this when she began appearing in many games, and it became very obvious after she became playable in 3D World and Super Smash Bros.. She's either considered a unique character who is a great addition to the franchise, or as an overrated knock off of Peach who receives too much attention when other characters could be getting it instead.
Waluigi to a pretty big degree. Those who hate him say he is a ridiculous Satellite Character with his sole reason or purpose to exist being to pad out the roster. Those who like or tolerate him say that his ridiculousness and pointlessness is the very essence of his character. And it goes on and on. He's never been featured in a non-spinoff Mario game until Super Mario Maker (as a Costume Mario power-up). There's also a subset of hardcore fans who generally dislike the Mario spinoffs to begin with. However, thanks to Alternative Character Interpretation , getting some good stages and music to his name, and getting his character taken in an overall hilariousdirection, he's been somewhat Rescued from the Scrappy Heap and become a Base Breaking Character Ensemble Dark Horse in his own right, enough for people to actually get mad when he didn't appear in Mario Kart 7.
Pauline is a mild case of this as there are those who wish Nintendo would finally let her have a bigger role in the games especially since she was Mario's original love interest while others don't simply care for her and argue that she just wouldn't fit in with the Mario series anymore. But at least Pauline still gets to occasionally appear in the Mario vs. Donkey Kong games. She also became extremely well-liked to the point of becoming an Ensemble Dark Horse with the revealed that she's the mayor of New Donk City in Super Mario Odyssey.
The Koopalings have shifted from Ensemble Dark Horses to this largely thanks to spending three2D platformersin a row as the end-world bosses, with Paper Mario: Color Splash adding an RPG offender to this trend as well. While they're still loved for being a Quirky Miniboss Squad with distinct appearances and quirks, and for Mario & Luigi: Paper Jam giving them more dialogue and not making them take up the roster of every major boss fight, a portion of the fanbase believes that they are becoming overexposed and are a large sign of the lack of creativity in the New Super Mario Bros.-based games. Wishes for the franchise to have more original bosses like the firstNew installment have also been on the rise just about every time they are confirmed to make an appearance.
Removed these entries because they were already listed on EnsembleDarkhorse.Super Mario Bros, and a Base-Breaking Character can't be both. Please see the Base Breaking Character Clean-Up Thread
if you wish to add them again.