For the planet, please see Kei.
Kei was a person mentioned in the Treaty of Armens, together with Yuri. The treaty described them as "the two cute girls with the big guns." Rick was responsible for including them in the treaty. (TNG: "The Ensigns of Command")
This character was only mentioned in writing.
Kei and Yuri were references to the Japanese Anime
(Japanese animation) series Dirty Pair.