On Halle Bailey's Ariel and the Egyptian 25th Dynasty
Disney recently announced that Halle Bailey, an African-American singer and actress from Atlanta (represent!), has been cast as Ariel in a live-action version of the Disney animated classic The Little Mermaid. Although I haven't seen any ugly commentary on social media about it myself, I have heard some people are getting upset and I can easily imagine this being true, either due to authenticity concerns about the source material, straight-up racism, or other issues.
Firstly, although The Little Mermaid is based on a Danish story (by author Hans Christian Anderson), the mermaid civilization is not connected to my knowledge to Danish society in any significant way. If it turns out they're descended from Vikings mutated by some kind of magic let me know, but it's my understanding that's not the case. The mermaids could easily be migrants from somewhere else who settled in the vicinity of Denmark, perhaps due to the Medieval Warm Period making their original homeland in the Mediterranean or even West Africa inhospitable. Therefore, even though the landlubbers nearby are white, the mermaids could be Semitic or even black. Although I'm generally not a fan of "if it's fantasy it doesn't have to be 'realistic'" attitude, the above explanation is a plausible one for a large Middle Eastern or black (mermaid) population in an otherwise European setting. After all, the Gypies (whose actual name for themselves is Roma or Romany) are originally from India and the Hungarians are a Turkic or Finnic people originally from Russia.
Secondly, even if the mermaid population generally is of European in appearance, ruling elites don't necessarily match up with the local population. Much of northern England was ruled by Vikings for awhile, the whole of England was ruled by different French dynasties from the Norman conquest of 1066 until the Welsh Henry Tudor took power in 1485, parts of or all of China were ruled by non-Chinese steppe peoples on many different occasions, etc. More appropos would be the 25th Dynasty of Egypt--although the Egyptians were a Semitic people, the 25th Dynasty was originally from Nubia, much farther south.
So here's where it gets Game of Thrones. Triton is originally from somewhere else and is the founder of a new dynasty, either elected by other members of the mermaid elite after the previous king dies without an heir or who seizes power in some kind of civil war. As king he exiles Ursula, ostensibly for practicing witchcraft and other sorts of bad behavior but really because she's a member of the previous dynasty. However, not only is Triton foreign, but Triton is a widower with no interest in remarrying and has only daughters, no sons. This makes his regime vulnerable and Ursula plays on Ariel's interest in human culture as part of some kind of scheme to seize power.
Yes, that's needlessly complicated for a kids movie, but they did elaborate on the original Aladdin to make the new live-action version more elaborate (Jasmine seeks to become the next ruler of Agrabah in the vein of Razia Sultan, the only female ruler of the Muslim Delhi Sultanate, Jafar is a "street rat" himself who rose to become the grand vizier). If this is too much and if Disney wants to keep Triton as a white Zeus-alike, they can always depict his late wife as being black and Ariel takes after her mother rather than her father in looks.