Gart Default is the main antagonist from Robot and Monster. He is Robot's arrogant and overbearing older brother and his supervisor.
He was voiced by Maurice LaMarche.
Gart is Robot's rival since he was born. Unlike his younger brother, Gart has four-fingered hands, which he has taken advantage of by constantly beating Robot in games of Rock, Paper, Scissors, as Robot is only capable of using scissors due to his pincher claws. By his tenth birthday, Gart inherited the Blinking Light Factory from his father, and has since became successful in nearly everything he's done. According to Gart in the episode, "Between Brothers," Gart apparently was the favorite of the two Default children, while Robot was the black sheep of the family due to his inventions not working properly.
Despite feeling superior to his brother, Gart still hired Robot to work in their father's factory as part of quality control, along with Robot's best friend, Monster. As a boss, he's cruel and ruthless, having many rules against any sort of relaxation or comfort within the factory. He also openly torments his employees (particularly Robot and Perry), and, in case of an injury (such as a severed limb), has a policy that prevents injured employees from going to the hospital during their work hours.
His office is large and spacious, with pictures of relatives (though notably, Robot's picture does not appear) on the walls. His desk can sink into the floor to make it shorter or climb higher towards the ceiling in order to appear more intimidating. A wallscreen behind the desk usually shows a black void with large flames burning. This is for intimidation. The screen can be changed (as shown in the episode, "Blinking Light") to different views, even a happy, bright field with double rainbows in the sky. It is evident that Gart's employees dislike him (except for Monster), but they work for him because they need the money.
He appears to be somewhat of a miser, as revealed in "The Prince of Scamtown" that he refused to loan Robot money because he needed it to "wipe his butt"; but he does spend his money for the price of seeing his brother suffer.
In "Between Brothers," Monster invited Gart to his and Robot's apartment for dinner, in an attempt for the two Defaults to become friends. However, this ended badly when Gart bought the apartment building from Mr. Wheelie, becoming the new landlord. As landlord, he harassed and tormented Robot and Monster by turning off the heat, turning the heat up too much, and even giving Ogo the ability to host fire drills whenever he pleased (even very early in the morning or in the middle of the night). Robot fought back finally by challenging Gart to a contest (in which Gart picked Rock, Paper, Scissors), and won by inventing a device that literally summoned a piece of paper to cover Gart's rock fist. Gart gave the building back as promised afterwards.
Though Gart is very arrogant and mean, he usually does seem to keep promises (as he did give the apartment back, and did give Robot money for his internal gyroscope in "The Prince of Scamtown"). Gart seems to love nothing more than seeing Robot fall flat on his face and lose contests, and is not afraid to rub his success in Robot's face, such as when he utterly humiliated him when Robot sacrificed his chances of winning the two-colored blinking light contest to Lucy in order to save Ogo in "Ogo's Friend."
Being related to Robot, his appearance is very similar to his younger brother. Notable differences are that he's larger than Robot, and instead of a total of four wheels, Gart has six. Gart also has, as previously stated, four-fingered hands. His antenna is straighter than Robot's. Instead of orange, Gart's body has a more golden color, and the hatch on his middle sports a yellow capital "G." Unlike Robot's eyes, which are yellow, Gart's eyes are pure white with black pupils.
- He has a "G" on his chest plate to let people know he's Gart and not Robot.