Despite his master's harshness, his stubborn nature, and reluctance to have fun with him, GIR is genuinely cheerful and playful. Sometimes he bends Zim to his own will, which allows GIR to get away with some of his antics. In Bad, Bad Rubber Piggy, GIR grows tearful when Zim is taking away his rubber pigs, but upon feeling sorry for the robot, Zim lets GIR play among them for a while. Additionally, in Walk of Doom, GIR gets them both stranded in the city; at first, Zim is enraged with GIR, but when faced with GIR crying, Zim forgives him surprisingly quickly. In Tak: The Hideous New Girl, Zim reveals that he promised that GIR could rule the moon after their conquest of Earth.However, their bonds of loyalty to each other are not always strong. In Nubs of Doom, Zim tried to rid himself of his SIR Unit by replacing him with a new assistant named Minimoose. Although this plan does not go smoothly, Zim does tell GIR that he is "horrible". GIR, however, is not upset by this insult. In Roboparents Gone Wild, GIR leaves behind a helpless Zim in favor of fun and chaos. Despite a pleading and rather desperate look to his robot, GIR fails to save his master from being ousted.
Some of the ways that Zim interacts with GIR may be explained by the concept of irken defectives. If Zim is at all concious of being a defective (which is unclear in the series), he may recognise something familiar in his defective SIR unit, accounting for the softer way he sometimes treates him.
Their relationship can be seen in almost every episode, however a few have critical points in their development.
- Walk of Doom
After realising that GIR left his guidance chip back at the base, Zim snaps at him. GIR, who just ate his cupcake, begins to cry. Zim misinterprets GIR's tears as a guilty apology and tells him "I see that you understand your mistake GIR, and me being angry will get us no closer to home." However, GIR was really upset because he missed his cupcake. This is one of the few times Zim shows remorse for his mean treatment of GIR.
- Battle of the Planets
Zim shows respect for GIR after the robot pressed buttons on Dib's ship, messing up his flying controls. He expresses this by saying, " Maybe that little robot isn't such a bad evil minion after all."
An example of GIR's total disregard for Zim's reprimanding is when Zim goes on a germophobic rampage. GIR, oblivious to Zim's newfound paranoia of germs, insists on hugging him while smothered in bacteria.
- Invasion of the Idiot Dog Brain
When Zim first realizes that GIR is unresponsive, he sounds mildly concerned. However, the mess that GIR makes of the ensuing situation undoes any concern Zim may have had for his robot.
- Halloween Spectacular of Spooky Doom
When Zim escapes the Nightmare version of Skool, he expresses concern for GIR's safety, saying "I only hope poor GIR is alright by himself".
- Bad, Bad Rubber Piggy
GIR hides dozens of rubber piggies inside his head, hoping Zim won't find them and that he would get to play with them; otherwise they would be tossed into the Time-Space Object Replacement Device. Zim only has to give him a suspicious look for GIR reveal the piggies, but an equally sad look from GIR makes Zim allow GIR to play with them before he sends it into the past.
- Walk for Your Lives
- GIR is surprisingly helpful and focused in this episode, up to a point. He helps Zim get the slow explosion down to the Voot hanger but quickly returns to his destructive antics when Zim blames him for damage to the base. When Zim decides returning the explosion to the proper speed is the best course of action it is GIR who acknowledges the danger and speaks up "won't it get real bad?" but Zim ignores his advice.
- When Zim decides to fix GIR's behavior glitch, GIR shows what may be his true colors, but this is uncertain. GIR tells Zim that he cannot stand him, and sees him for the woefully inadequate leader and master that he is. This could either be a result of Zim's frequent bad treatment of the robot, or a change in GIR's personality after being 'fixed'. When asked if GIR remembered his time of servitude in the past GIR responds coldly with, "Yes. I didn't like it." This shows that serving Zim is frequently more of a hindrance than a pleasure to GIR. The creator of the show, Jhonen Vasquez, is quick to note in the commentary for Bestest Friend that GIR just wants to die and actually hates life. This may back up the reason for such hatred and strong, angry feelings toward Zim in GIR goes Crazy and Stuff, or may be the result of personality alteration.
- When Zim sees GIR's dog disguise lying down with beef oozing out of the zipper, he thinks that GIR has turned into ground beef and cries, until the real GIR jumps out from behind the couch.
- On occasion, Zim has even been shown to look to GIR for reassurance: When they stop by Dib's house to borrow Dib's telescope, Zim gives GIR a worried glance, which GIR returns with a smile, a thumbs-up and a happy squeal (When Zim turns his back, however, GIR gleefully pretends to squish his head between his forefinger and thumb, since Zim is in a distant background).