Kodos

Kodos (pronounced Koh-dohs) is a Rigellian from Rigel 7. She is the sister of Kang. Kodos has been referred to as both male and female. Together, Kang and Kodos try to take over Earth and are usually seen attacking Springfield.

Kang & Kodos have a lot of space weaponry at hand and have their own spaceship. They speak the Rigellian language, which, by coincidence, is identical to English. Although they look identical, Kang has a deeper voice than Kodos.

History
Kang and Kodos once impersonated Bob Dole and Bill Clinton respectively in order to become elected President of the United States. When they were revealed to be aliens, they were still more popular than a third party.

Kang and Kodos have both ruled over Springfield until they were found out to not be welcome and fled from their primitive weapons.

Trivia

 * Kodos has been referred to as both male and female. Female in Treehouse of Horror VII and male in Treehouse of Horror XVIII, though this may be due to humans being unable to tell male and female Rigelians apart. Also, Kodos mentioned his/her "700 testicles" in "Treehouse of Horror XVIII", however, in Treehouse of Horror XXII, Kamala, a female Rigelian, also made a reference to having testicles.
 * In several DVD commentaries, Matt Groening and other writers confirm that Kodos is indeed written as female, as consistently as possible.
 * Matt Groening had an idea about Kang and Kodos appearing on Futurama, but strangely they never did.
 * In the video game, Simpsons Hit &amp; Run, Kodos works with Kang to make an Intergalactic reality show in Springfield, Foolish Earthlings and is killed in the production due to the actions of Homer's plans of using nuclear waste to destroy the UFO.