Fan Casting Ambiguously Asian in Sort by Tropes

Either a character that is either Asian or miiight just be someone with dark hair and eyes, OR a character is definitely... probably? of Asian descent. Which part of Asia? Just Asia. It can't have THAT many countries and that much variety, right? What's that? There's 4.5 billion people living all across Asia, all with different appearances and from different cultures? Oh, well. We have someone who looks kinda Asian. That'll work, right?