Extra-terrestrials are used to make point about immigration and discrimination. No it’s not District 9, it’s Yoshitoshi ABe’s NieA_7.
Probably the show that has the smallest gulf between the whimsy and humour of ABe’s art and writing and what ends up on screen, it’s also overlooked compared to Lain and Haibane Renmei. Going back to the first episode this week, it wasn’t quite as good as I remember (except the music, which is a great collection of ragtime), but it’s definitely worth a look if you’ve not seen it yet. Certainly one of the better TV anime from 2000.