Back when Super Smash Bros. for Nintendo 3DS was launched, players quickly pointed out that the inside of Princess Peach’s skirt was cloaked in darkness. The same is true in the recently released Super Smash Bros. Ultimate, but not for all characters.
For example, in Super Smash Bros. Ultimate, the same privacy void Peach gets (see below) is also afforded to Rosalina. Inevitably, some folks have been trying to figure out workarounds.
Oddly, however, Palutena does not appear to get the same treatment—at least, in the Japanese release.
Not sure why!