Super Mario Wonder is bringing Princess Daisy back to the mainline Mario platformers for the first time since her debut all the way back in 1989's Super Mario Land. But why now, and why Daisy? She's a popular spinoff character, but so is Waluigi — and unlike him, Daisy doesn't have meme culture behind her to drive her popularity. So why is she suddenly in Smash Bros. and a mainline platformer? The answer is actually pretty simple: she's a female character with personality in a series devoid of much characterization in general.
Source：https://www.cbr.com/so-whats-princess-daisys-deal/
