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.

History
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.