4101-4102. Kang and Kodos

Kang and Kodos are a duo of recurring characters in the animated television series The Simpsons. Kang is voiced by Harry Shearer and Kodos by Dan Castellaneta. They are aliens from the fictional planet Rigel VII and appear almost exclusively in the "Treehouse of Horror". The duo has appeared in at least one segment of all twenty-one Treehouse of Horror episodes. Sometimes their appearance is the focus of a plot, other times a brief cameo. Kang and Kodos are often bent on the conquest of Earth and are usually seen working on sinister plans to invade and subjugate humanity.
The duo first appeared in season two's "Treehouse of Horror". The first drawing of Kang and Kodos came from writers Jay Kogen and Wallace Wolodarsky. The finished design was based on an EC Comics issue cover. Kang and Kodos had brief cameo appearances in several non-"Treehouse of Horror" episodes and have appeared as villains in several of The Simpsons video games.

Kang and Kodos first appeared in the second season in "Treehouse of Horror". The idea of Kang and Kodos came from Jay Kogen and Wallace Wolodarsky, writers of "Hungry are the Damned". In the script, Kang and Kodos were shown as "an octopus in a space helmet with a trail of goo". The finished design was based on EC Comics cover issue. Although originally designed to constantly drool, Matt Groening suggested that they not drool all the time to make the animation process easier. However, the animators did not mind the work, leading to the drooling staying in the script. Kang and Kodos's names are derived from two Star Trek characters. Kang was a Klingon captain portrayed by actor Michael Ansara in "Day of the Dove", whereas Kodos the Executioner was a human villain from "The Conscience of the King".Harry Shearer voices Kang, and Dan Castellaneta voices Kodos. An unofficial rule for the writers is that Kang and Kodos must appear in every Halloween episode. Despite this rule, the writers say the duo will often be forgotten and are added at the last second, leading to brief appearances.

Traditionally, Kang and Kodos appeared in every single Treehouse of Horror episode as a part of a story's plotline or as cameos. They almost did not make the cut in "Treehouse of Horror VIII", but David X. Cohen managed to persuade the producers to keep the scene. Kang and Kodos were originally going to make regular appearances in the show. One idea was only Homer would be able to see them and everyone else thinking Homer is crazy when he talked about the aliens. However the concept was "too far out", leading to characters only featured in the "Treehouse of Horror" specials. In some appearances, Kang and Kodos will laugh hysterically for several seconds. This was suggested by Sam Simon. During production, the episodes would often be too short; so to make more time, their laughter was lengthened.
Kodos's gender has come into debate from fans. In "Treehouse of Horror VII", Kang introduces Kodos with "This is my sister Kodos". The line was pitched by George Meyer and was even somewhat followed in later episodes as the writers tried to make Kang the more dominant of the two. In previous and subsequent episodes, Kodos has been referred to as a male.