- "But I need tacos. I need them or I'll explode. That happens to me sometimes."
- ―-- GIR asking for tacos
GIR is the good natured, hyperactive robotic assistant given to Zim upon his being sent to Earth by the Almighty Tallest. GIR, who often acts erratically in an almost child-like hyperactivity, was put together using an assortment of scrap parts as a deliberate act of sabotage by the spiteful Tallest. Instead of a SIR, the standard robot issued to Irkin invaders, Zim was assigned GIR due his mission being little more than an effort at getting rid of him.
The somewhat innocent and child-like GIR is voiced by Rosearik Rikki Simons in the show and serves as Zim's constant companion. He is seen as a bumbling and often unhelpful assistant who occasionally hinders Zim's efforts on Earth through his erratic hyperactive actions. GIR differs from regular SIR units in the colour of his luminous eyes, shoulders and chest panel which are teal instead of the red seen on SIR units. He also lacks the facial groove seen on SIR robots and seems to be much more simply designed as a result of his being hastily put together as an insult aimed at an oblivious Zim. GIR also has a visible mouth while a SIR robot does not. The similarities in his design suggest that he was put together using scrap parts from an older SIR model by disinterested Tallest. Deployed on Earth the bumbling GIR assumes a dog disguise wearing a zip-up dog suit in an effort at concealing his identity - which he frequently counteracts by acting in a very un-doglike fashion.The disguise is made up of a green "dog suit" with black ears, a zipper on the stomach and a head that is worn like a hood. It also features a tail which GIR is able to wag in order to mimic an Earth dog. The suit's large eyes sometimes blink but often stare blankly at whatever GIR is looking at. It's mouth occassionally opens when he speaks whereas at other times it will stay closed. This suggests that the disguise, like GIR, is defective.
GIR is extremely hyperactive and child-like in many ways. He will eat nearly anything that is put in front of him regardless of whether it is actually edible. He normally spouts continuous strings of nonsene but does have a few brief moments of intelligence speech - such as when he considers whether making an explosion speed up will make things better or worse in the episode "Bad, Bad Rubber Piggy". When given an order by his supposed master GIR will usually mess around or go straight back to what he was doing when Zim leaves the room. Occasionally, GIR will actually carry out an order as expected of a robotic assistant.
Zim has described GIR's intelligence as "bad" and the hyperactive robot is a major reason why Zim's efforts very frequently fail. He has been known to outright disobey orders if it means that he won't get something he wants such as food or his beloved rubber piggies. Unlike his master, who hates a great number of people and things, GIR approaches nearly everything in the world with immense affection and enthusiasm. Despite the way in which he frequently disobeys orders and hinders Zim's efforts GIR is extremely loyal to his master.
- While SIR units stand for "Standard-issue Information Retrieval" units, the "G" in GIR's name has been confirmed to stand for "Garbage". In that case, his name means "Garbage Information Retrieval" unit. This may mean he used to be a garbage droid that was shut down many years ago and is now dysfunctional due to all the years he's spent in the trash bin.
- Zim's mission to Earth was never intended to actually be a serious invasion or even of any importance at all. This explains why Zim was not assigned the standard SIR unit as the Tallest likely didn't want to waste important hardware on the Irkin they despised the most. As a result, Zim was given GIR as a substitute for a helpful robotic assistant.