Mario Kart 8 boasted the most characters that the series had seen yet. However, it was stuffed with all of the Koopalings and unnecessary alterations on existing characters (cough, Tanooki Mario, cough). While most of them are just annoying, there is one who just makes no sense whatsoever: Baby Rosalina.
existence of Baby Rosalina is a little controversial enough, but we'll let it slide knowing that she does have an origin (as shown in Super Mario Galaxy 2). Where the two stories contradict is where it's shown that Rosalina had red hair as a child, but in Mario Kart 8, is depicted with yellow hair and a blue dress, like adult Rosalina. It's not continuity breaking by any means, but it's different enough to raise an eyebrow.