Vortian

"Zim loves Vortians. He knew that the Irkens were used to be allies with the Vortians before things get out of hand when Larb did it. Guess that's his fault of course."

--Su Ji-Hoon, Dirty Little Secret

Vortians are a highly intelligent race of scientists and engineers who inhabit Vort.

Biology and Appearance
Vortians have digitigrade legs with elongated tarsals. As a result, Vortians walk on their "toes" as opposed to their entire feet. However, their feet lack toes and seem to be pointed at the end. They have "horns", which are likely more like shelled tentacles as they are mildly ambulatory as opposed to stiff. They have tiny eyes of a single color, and their heads are large, and shaped vaguely like that of an Irken.

It is shown that Vortian skin can come in  small variety of colours, but these appear to be predominately greys, pinks and muted blues.

Their species doesn't appear to have much sexual dimorphism, although there is only one known female Vortian to compare to the rest. Vortians resemble goats in some ways, just as the Irkens resemble insects, though it seems unlikely that Vortians have any particular mannerisms reflecting that of goats, unlike Irken society's very insect-like layout.

Vortians may be carnivorous. The only Vortian food shown in Invader Zim are "Vortdogs" sold at Shloogorgh's Flavor Monster, which are presumably made of meat-like earth hotdogs. Vortian teeth are also sharp and jagged, suggesting a carnivorous diet. Vortian tongues are segmented similar to Irken tongues. Vortians are rather short, about the same height as Irkens. It is unknown if their society is based on height, but it seems to be unlikely. It may be that Vort's leaders were elected, like Earth's.

It has been revealed that Vortians have the ability to reproduce, as Vortian children are seen in the first issue of the Invader Zim comics.

Invader Zim (Before World War III)
Vortians are very industrious creatures, and have a history of being allied with the Irken Empire. During this time, they worked with Irken scientists to create high tech military gear and weapons of mass destruction. However, in "recent years" Invader Larb conquered the planet Vort, effectively turning it into the Irken Empire's top military research prison.

Not all Vortians are prisoners though; some have escaped and can be seen briefly on planet Foodcourtia. Eric the Blob mentioned that he had installed similar security systems to the one in Shloogorgh's Flavor Monster in Vortian prisons, but they were discontinued after multiple Vortian prisoners escaped by "hiding deep in garbage cans". This could explain Lard Nar's freedom and could pose as an excuse as to why there may be any free Vortians.

Vortians created devices such as the MegaDoomer, as well as the doomsday technology inside of Minimoose and the Vortian liquid substance used for the Santa Suit. However, it is suspected the Vortians have shown small signs of rebellion by purposely flawing their creations. For example, the Vortian-designed MegaDoomer cloaked itself but not the user.

Also worth noting is that Vortian Prisoner 777, an acquaintance of Zim, was willing to hand over the Massive's schematics with very little convincing needed, despite the fact that he knew and openly stated that it would infuriate the Empire. He also was planned to provide the experimental doomsday technology for Zim when he was creating Minimoose in the unfinished episode of Invader Zim, "Nubs of Doom." Though when the comic series was released, 777's cooperation was briefly explained - it was revealed in issue 1 that Zim has 777's children hostage and threatens to erase them if he doesn't meet Zim's demands.