He was voiced by Max Burkholder.
He is originally known as the "Tyrant King". World only appears to only be a pair of eyes and a mouth who has the ability to possess and control only one thing at any time he wants by latching onto it, but is actually the entire world in the toy chest and has complete control over it, even destroying it in a fit of rage. He has been living in a toy box and causing trouble for his creator's parents and is forced to live at Foster's in the attic until Frankie, refusing to let an imaginary friend remain locked in a toy chest, decides to open the chained-up toy box. When Mac, Bloo, Wilt, Coco and Eduardo discover she is missing, they fall into the toy chest to rescue her. They ask around a small town if anyone has seen a woman of Frankie's description but nobody responds. A group of weeble policemen discover they have entered the world and chase after them, but the gang are saved by a heroic man. He tries to warn them that their pursuit of Frankie will lead through extremely dangerous environments, but they are determined to rescue her. They fall off a musical and colorful bridge, get chased by their zombie-like doppelgangers through a Super Mario World-like environment and go to the house of a toy dog, where they are set up for a trap to eat crumpets with sleeping powder. Mac does not eat the crumpets (since the sleeping powder was thought to be powdered sugar, and he can't eat sugar without temporarily losing his mind) and is able to save the others. As they try to escape, they discover that the policeman, heroic man, and toy dog are all controlled by a single face—World—who can animate and control seemingly anything he latches onto. World is trapped on an apple and the gang leaves it at a desert; but latches on a horse, truly the guise of Mac and the gang rides by, and World is able to move once more. It gallops off to the castle, where the gang find Frankie and attempt to save her. However, Frankie reveals that World never kidnapped her, she was staying of her own free will and is happy to be away from the work at Foster's and Mr. Herriman's constant nagging. The friends attempt to console her, but World gasses them and they fall asleep. When they awaken, they find themselves in a fake version of Foster's created by World, who shrank them into it. When Frankie discovers them shrunk, World finally becomes upset and scolds Frankie of planning to leave him alone in the toy box forever. She calms him down enough to befriend and unshrink the gang, but Mr. Herriman bursts in, having gotten into the toy box and somehow past the gang's obstacles, and harshly scolds World before preparing to take the gang home and leave World. World's world falls to pieces until it's nothing but a white void. World becomes angry and unstable and turns into a chimera-like creature to attack them all (made of the remaining refuse of his world). The gang manages to escape the toy box. Frankie climbs out as well and tries to convince everyone to let World out of the box, which they reluctantly agree to do. World reforms happily and shouts that he's free. Frankie tells the gang that all he wanted was a friend all along. World adapts to the new environment and lives as a stuffed rag doll in the home.
World can be best described as happy and rather enigmatic due to his many different bodies and a bit of a prankster but well meaning most of the time. However, if upset, he can become quite clingy, monstrous, and vituperative, especially when he thinks he might be abandoned. This is mostly notable when he plays hide-and-seek with Frankie, panicking and crying when he thinks he might have lost her, thus establishing his moments of instability that reappear in the film. For example when Frankie discovers that he shrunk Mac and the others, he starts to get angry causing the world to shake and he begins to rant that Frankie is going to leave him just like "they" made "him" leave him all alone, with Frankie quickly figuring what he means and calming him down. He even morphs into a giant monster due to the fact that Mr. Herriman was telling him, he was going to be alone, that was something that really shattered his heart, and made him burst into rage.
Grim Adventures of Billy & Mandy