Gazlene "Gaz" Membrane is a vicious and vengeful anti-hero and one of the main characters on the cartoon Invader Zim. The name is short for Gazlene, a play on the word gasoline.
Gaz is the younger sister of Dib and is a dark, brooding, and anti-social girl that only likes video games, books, and pizza. She is often either annoyed by or indifferent to Dib's obsession with the paranormal and his rantings about Zim being an alien. She does in fact know that Zim is an alien out to conquer earth, but thinks that he is too incompetent to succeed.
Gaz is generally a girl that is nice to a small number of people, her workaholic dad included. When she is angry, however, Gaz becomes a furious bringer of vengeance, mysteriously capable of supernatural powers such as levitation, pyrokinesis, and umbrakinesis. In this state she is extremely violent-minded, threatening whoever angers her with fates worse than death. She also controls an army of robotic animal dolls equipped with deadly weaponry. They are her "security guards" and are trained to eat human flesh (or so she says).
Despite her dislike for her brother, she sometimes helps him in his quests, but only when it benefits her.
Gaz is shown to easily be able to thwart any schemes by the show's Antagonists (Zim, Tak, Etc) with absolute ease. She was able to destroy Zim's base on multiple occasions, and defeated Tak by splashing her face with soda (She did this to Zim earlier in the same episode as well).
All of this has made the character of Gaz controversial, and was criticized by many Christians when the series first premiered. In spite of her dark nature and misanthropic attitude, her voice actress Melissa Fahn is actually quite sweet and pleasant, and she has confirmed that Gazlene can love and have positive emotions; Gaz just simply has a big ego and thinks she's better than everyone else, hence her attitude and demeanor.