Rigel 7

Rigel 7 is a planet home to the Rigellians, including Kang and Kodos. They speak Rigellian, which by coincidence, sounds exactly the same as English. The other inhabitants of Rigel 7 seem to be similar in appearance to Kang and Kodos, and include, amongst others, Serak the Preparer, and presumably Mr. Sulu, the Submarine operator of the U.S.S Jebediah.

Non-canon
People from Earth travel to Rigel 7 in order to obtain Hillarium. Eventually, a massive war between the Rigellians and nature and the humans takes place with the Rigellians winning the war and all the humans being defeated.

Behind the Laughter
The planet is a parody of the one of the same name from Star Trek.