Soon after his birth, a little smeet named Zim shoved Grim up a tube. This simple event was not only a crucial moment in the history of Grim, but the history of the entire planet. The tube led directly to the planet's power core, and Grim's PAK was lodged into one of the main gears, shutting down the planet's power for five years, creating "Horrible Painful Overload Day." Grim miraculously survived, and most of his PAK was salvaged. But not all. Some information in his PAK was damaged, and that happened to be the information from the Control Brains. Being: the bloodthirsty desire for conquest, faith in a height- based heiracy system, and many other common Irken beliefs. This caused him to be very unique and independent minded, and loathe military training. Grim soon befriended the only one as misunderstood as he was, and the very reason for his unique worldview: Zim. The two were inseperable. Inevitably, Zim had to leave for military matters. Soon after, the Tallest Miyuki and Spork mysteriously died, and the time came for a new Tallest to be selected. Though Grim disliked the concept of having a Tallest, he saw this as an opputunity to turn the Irken Empire in the right direction. He had always been extremely tall, and was about to be officially declared Tallest, when [Red] and [Purple] came in at the last second and stole his chances, despite Grim being told that no late submissions would be taken. Thus, he developed a powerful grudge against the current Tallest.
After an unspeakable crime against the Almighty Tallest, Grim was sentenced to live on Earth with Zim, something that was supposed to be a worse-than-death sentence. If he is more than a mile away from Zim for 24 hours, he'll explode. Even so, he's managed to create an online empire/wiki called the "Grimmy Empire," and has become ruler of the Neptunians, nicknaming the planet "Grim's Magical Wonderland of Awesome Junk and Toxic Gases" (Due to Neptune's poisonous atmosphere.) He also frequents the Swollen Eyeball Network as "Agent SecretAgentMan".
Grim is tall, (around 5'5") and refuses to wear an Irken uniform because it shows servitude to the Irken Empire. The uniform he has looks like Zim's. He resents the fact that that his entire life is riding on a backpack (The PAK) that is questionably functional. He wears a T-shirt with a grey alien head on it, both to annoy his skoolmate Dib and out of humor. This shirt is custom tailored to allow his PAK to potrude from the back because it "looks awesome!" He has Green eyes and unusually long antennaes, and for his disguise wears a blonde wig and blue lenses.
Grim is very laid back, yet shy at the same time. He is more of a man of action, and doesn't talk much unless cracking a joke. He is very artistic and loves to draw. He is also very scientificly gifted, and was a Vortion scientist with Zim.
LIR is Grim's SIR. His name is an acronym for Limited edition Information Retreival unit. He was bought by a questionable dealer in a dark alley, and Grim soon regretted purchasing him due to him being highly unstable, much like GIR. LIR's body is oval-shaped instead of humanoid, and his eyes generally glow orange instead of teal. His jets are in his hands as well, instead of his feet, and he has two antennae. He is disguised as a teddy bear with a striking resemblance to Shmee from one of Jhonen Vasquez's comics.