Schrödinger's Skirt

Mostly used in reference with anime characters of typically traditional feminine traits, specifically wearing the clothing apparel known as skirts. This term implies that no one knows what is under the skirt and whatever is under the skirt is the observer's choice, implying the aforementioned anime character might be a femboy or an actual girl, or perhaps an all devouring eldritch being. This term was arguably first used by semi-popular American/Serbian YouTuber LivingIronicallyInEurope, in reference to his YouTube account's PFP.

John: Man, hentai's so confusing nowadays, you never know who's a girl and who's a boy.
Rohn: I know, everyone's wearing a Schrödinger's skirt.