Since Invader Zim is a crazy show, it stands to reason that there are some crazy theories about Zim and all the Irkens. Invader Zim fan theories range, from seeking to explain the PAKs the Irkens wear all the way to connecting the universe to Toy Story. And more than one theory aims to explain the reproductive practices of these strange aliens.
While few people consider Invader Zim to be one of the greatest animated shows of all time, it does have a loyal following and is sometimes mentioned in the same breath as Rick and Morty. For those who aren't familiar, Zim is an alien of the species known as Irkens, seeking to infiltrate and conquer Earth, but his own stupidity and that of his companions often makes that goal nigh impossible.
These Invader Zim theories from Reddit and other such communities ask deeper questions about the Irkens and their human counterparts. Are they all as dumb as they seem?
From Redditor /u/yay855:
Invader Zim was known for its very stupid characters, disgusting imagery, and all-around disturbing elements. I propose that we are seeing the world how Zim sees it.
Zim is a highly advanced alien; to him, all humans are deformed morons. The only exception is Dib, whose features are closer to Irken than human and who is one of the smartest people Zim had ever met. This is because his father genetically engineered him to be a genius, but something went wrong, causing deformities but allowing him to see the 'supernatural' elements that others ignore.
The cities and food is so disgusting because Zim comes from a more clinical people. The Irkens are created, not born, and likely live in a much more sterile and orderly environment. Compared to that, and the food they eat (pre-packaged snacks, mostly), Earth's urban environments and food is disgusting, and filled with way too much grease than is healthy.
From Redditor /u/UOUPv2:
I think that in terms of science Zim is a genius, replacing a man's brain with an octopus' brain and improving the accuracy of an Irken GPS chip for example. Though when it comes to bring a soldier and a spy Zim lacks all the qualities like when he thought the tallest were honest about GIR being advanced or when he decided to ditch Dib by flying through an asteroid field. Being chosen for the first invasion had to be a great honor and being so short meant he only had to prove his worth that much more. Zim may be a great Irken scientist but what he really wants is to be a great invader.
From Redditor /u/mateogg:
Dib is a genius. He's incredibly good at computers, but the rest of the children his age are shown to be average, if not dumb. He also does really well in the test to enter his father's show, even though he is insecure about the parts about Dr. Membrane's obscure life trivia (the other part of the test is all science. Since he got a 94.1, I think, then he probably got a perfect score in the Science part). Most importantly, he's immune to Tak's technology and, according to Tak, it's because of his superior intelligence.
It's also possible this is why Dib is paranoid (just because he's right about Zim it doesn't make him less paranoid, specially since he already was into all the supernatural stuff before meeting Zim, and since there are various mentions of him mistakenly taking something natural as supernatural) and why he has a huge head (though in my opinion is not that large compared with other heads in the show, the size of his head is a running gag on the show).
From a TVTropes user:
If the Tallest don't like someone, then it doesn't matter if they are a successful Invader. A conquered Earth would lead to the Tallest being direct about it, just like they did to poor Skoodge. Thus, Zim keeps up his charade of conquest to prevent himself from facing the fact that his own species doesn't want him. Thus, he constantly puts GIR in charge of the crucial part of his plans.