I think a lot of shows could learn a lesson from Invader Zim when it comes to alien character design. Like, in most cartoon when you see aliens most of the time aliens of the same race look the same (or have slight differences), the only exceptions I can think of are Steven Universe, Voltron and Futurama.
An then you get Invader Zim where EVERY SINGLE irken we’ve seen looks different.
Like, yeah, the ones that pay an important part on some episodes obviously have to look different so you can recognize them
But the crew went a step further, to the point where every backgroun character (characters that we’ve seen once or twice at most and aren’t even doing anything) look different from each other
(and this is just a small taste)
And! Female irkens ALSO look very distinctive from each other, just look at the three girls from above!
(tho idk how i feel about girls being differentiated from boys by eyelashes and curly antennae, but hey! I’m glad they also avoid the trope of giving them more “feminine” clothes to differentiate them from boys)
Despite having some clearly defined characteristic that identify them as members of the same race, and most of them wearing similar-looking uniforms, every single irken we’ve seen has different and recognizable proportions and face and body shapes. Idk, its not common to see this kind of diversity in alien character designs on a lot of cartoons and I honestly love it.