Igor is a Decepticon who appears in the live-action film continuity, specifically within the events of Transformers: Dark of the Moon. His background is a peculiar one, as he is not a conventional Transformer but rather a small drone or pet created by Megatron. He appears to be cobbled together from leftover or destroyed Decepticon parts, serving as a loyal but insignificant companion to the Decepticon leader. Megatron himself has a vague recollection that the head used to belong to one of his former soldiers, and concept art and other adaptations strongly suggest that this original component was the head of Long Haul, a member of the Constructicons. The novelization and comic adaptation further describe him as the disembodied, bouncing head of another Transformer, though the film depicts him with stubby limbs and a makeshift cane.

In terms of personality, Igor is simple-minded, cheerful in a twisted way, and utterly devoted to Megatron. He is not very bright, as his mental programming is extremely basic, having been designed to perform only two primary functions: to worship his master and to consume enough to survive. He is often described as being "miswired," which contributes to his erratic and crazed demeanor. He spends his time groveling at Megatron's feet, eagerly awaiting his return, and munching on whatever scraps of debris or minerals he can find. He seems to derive great enjoyment from this constant scavenging, always appearing hungry for more. His ambitions extend no further than being Megatron's pet, a role he is perfectly content with, as he is too small to serve as a warrior and too unintelligent to function as a spy.

Igor's role in the story is that of a background fixture and a testament to Megatron's state during the film. He is seen in the Decepticon refugee camp in Africa, where Megatron gathers minerals to feed him and other smaller Decepticon creatures known as hatchlings. Igor's presence serves as a pathetic symbol of Megatron's reduced circumstances, a far cry from his former glory as a powerful conqueror. Later, Igor travels with Megatron and Starscream to Washington, D.C., as they prepare to launch an invasion. His most notable action in the film occurs at the Lincoln Memorial, where after Megatron destroys the statue of Abraham Lincoln, Igor happily gnaws on the disembodied stone head.

His key relationships are almost exclusively centered on Megatron. Igor is fiercely loyal to his master, seeing him as his entire world, and provides a form of companionship that the sycophantic and treacherous Starscream cannot offer. While Starscream constantly seeks to undermine Megatron, Igor offers nothing but groveling adoration, making him a kind of reliable, if useless, backup for the Decepticon leader. Igor shows jealousy towards Megatron's other subordinates, once shouting "NO! My master! Mine!" when Starscream tried to get close. It is unknown what happens to Igor after the climactic Battle of Chicago. The comic adaptation shows him after the battle, staring up at the sky and wondering what has become of his master. At least one source suggests that he was not listed as deceased by the CIA task force Cemetery Wind five years later, implying he may have survived the war and gone into hiding, but his ultimate fate remains unconfirmed.

Igor does not undergo any significant character development within the film. His function is to be a static element of the environment, serving as a visual representation of loyalty and decay. He is not a combatant and does not contribute to the main plot beyond his brief appearance at the Lincoln Memorial. His notable abilities are minimal. He is a resilient scavenger capable of consuming and presumably finding sustenance in inorganic debris and minerals. His primary ability is his unwavering loyalty, which, while simple, is more genuine than that of Megatron's other followers. In the comic adaptation, he was seen being kept on a chain lead like a small dog, further emphasizing his status as a pet rather than a soldier.