GIR is the protagonist of Invader Zim. He is Zim's robot companion, constructed from scrap parts and given to Zim by the Almighty Tallest instead of a regular S.I.R. (Standard-issue Information Retrieval) unit. GIR is voiced by Rosearik Rikki Simons. The character GIR has featured in the main storyline in 2 episodes: "Invasion of the Idiot Dog Brain" and "GIR Goes Crazy and Stuff."
The point that GIR's body was first constructed is the first episode in the series (The Nightmare Begins). when Zim attempts to get a SIR Unit, a broken robot of a SIR was put together with parts from a garbage can by the Almighty Tallest and then put whatever they had in their pockets such as pennies, paper clips, and bubble gum into its head. The robot introduced himself as GIR. It is unknown what the G stands for, but it is theorized that it stands for garbage. he might be a SIR unit prototype, or an out-of-date model.
GIR is Invader Zim's robot servant, easily influenced yet impossible to fully control. He is incapable of focusing attention on important things for long periods of time and often speaks with no relevant coherent thought in mind, making him almost completely useless, or even disastrous. Occasionally he reverts to normal S.I.R. behavior, during which time either all his cyan colored components or sometimes only his eyes become red and voice becomes much deeper, but these periods are normally short-lived. During the episode GIR Goes Crazy and Stuff, Zim manages to set GIR to duty mode using a behavioral modulator, but the result is that he eventually sees Zim as a threat to the mission and tries to kill him. When GIR shuts down, all of his cyan parts turn gray and he reverts to lifelessness. As a robot, GIR technically has no gender, but he is usually referred to as being male, mostly by Zim. In public on earth, Zim and GIR must wear disguises, GIR's most common disguise is a green dog suit that squeaks, with a visible zipper down the front. Another disguise is one that looks like a human child, and another that looks like a government agent by the name of "government man". Unlike Zim, he doesn't mind getting involved with typical Earth culture, and has a strong love of Earth snacks, such as tacos, taquitos, waffles, cupcakes, chicken with mayo and slush-style drinks. A strange fact is in the opening for the show, when Zim is thrown into his voot cruiser, you can see GIR's eyes are green instead of cyan.