Kat is Tak's sister. Unlike Tak, Kat has a soft spot for Zim and wants to help him conquer the Earth. Kat does whatever it takes to help Zim, even if she has to destroy her friend Dib. She likes hanging out with Zim's robot, GIR, and eating taquitos and salty nuts. Kat doesn't like it when people mess with her friends, and they're found in Dib's toilet. Kat lives at Zim's house and wants to take over Planet Mars. Like Tak, Kat has a special ability, but hers can put anybody to sleep if they see into her eyes, but it only works with the average ones.
Kat doesn't go to Skool because she says she needs to protect GIR. All she does is look through Zim's stuff. Kat always seems do get into fights with other people and always wins. Kat has a robot named Nij. Nij likes pancakes and cherry poop. Nij is very advanced, unlike GIR, who is not stupid, just "very advanced". Nij dresses up like GIR to learn some of Zim's secrets, while GIR eats taquitos with Kat. Kat has sent love letters to Zim, even if he rips them up and throws them away. She sent one to Dib because of a dare from Zeita. Kat is the only one who knows where Tak is hiding. Kat sends her food everyday at the same time. Kat has a little crush on Dib. Kat wants to take over a planet to turn it into her playground. Kat tries to teach Zim how to love, but he is failing so far. Her and Dib been together for a while until she left him for Zim who likes Skittle. Kat is the sensitive type of girl.
Invader Kat's partner is Invader Shishi and their leader is InvaderPD.