Philip Chang sent his son into hiding while he was still an infant. Born in Hong Kong but raised in Seattle, Percival Edmund soon became known as "Grunge", an all-American slacker who knew little about his brave father. He was eventually invited to take part in I.O.'s Project Genesis, where Grunge soon found out he was in a prison-like breeding ground for Gen-Actives. Manifesting his powers, he escaped with his new teammates, a group soon to be called Gen¹³. They take a temporary break and Grunge travels with Freefall to Las Vegas, where he gets into trouble due to a high win rate. His abilities make it seem as if he and Freefall were statues.
Grunge is a skater/surfer and enjoys spending his afternoons sleeping in. Only Freefall appreciates him for who he really is. However this never stops Grunge from trying to hit on Caitlin Fairchild constantly, in many maneuvers that sometimes violate her right to privacy. Freefall initially goes unnoticed, despite her feelings for him and Rainmaker attempts to serve as the voice of reason for Grunge's attitude, going roundly ignored. Only after a weird episode involving a demonic entity attempting to consume his soul via a rare collector's comic edition, and Grunge's resulting dream in which he meets several characters from external comics series (Archie Andrews and his friends, the Teenage Mutant Ninja Turtles, Fone Bone and Spawn), does he realize both Roxie's and his own feelings for each other, and they begin a romantic relationship.
Despite his personal history, Grunge is dependable on the battlefield, listening to orders when given and improvising new ways to help. His sound system defeated the villain known as Helmut. When the girls were kidnapped by a toy manufacturer, Grunge used the properties of the toys themselves to help rescue them. After a notable round of cluelessness, Grunge travels to the desert alone and confronts a trickster deity who puts him through his paces. He is picked up by his friends, who believe he was just hallucinating everything because he did not bring enough water.
The interruption to regular life brought on by super-powers is normalized a bit when Grunge returns to school. He ends up with Caitlin in high level classes due to his photographic memory. His poor choice in new friends almost leads to the loss of old ones, as they do not like Rainmaker's more peaceful worldviews. It does lead to the release of an angry, super-strong simian that had been experimented upon in the school's laboratories.
Grunge's life is interrupted when I.O. forces blow up his house and slay the robotic housemaid. Grunge and friends travel to a small island where Lynch's friend is operating. Unfortunately the island contains a spaceship, which takes Grunge and Caitlin deep into space. There, he is affected by an alien system and goes on a rampage.
Grunge's second trip into space was not so far, only going so far as the moon in order to help out in the Fire and Heaven incident.
Grunge also appears in two text only Gen13 novels.In 'Netherwar', the entire team has to deal with International Operations cracking into hell itself.
Grunge appears as an agent of N.O.W.H.E.R.E. in issue 8 of the relaunched Superboy title. He battles Superboy, trying to kill him for escaping, as well as preparing for The Culling. N.O.W.H.E.R.E. also fitted him with mechanical implants to augment his powers, though they get ripped out by Superboy during their fight, leading to Grunge's defeat.
After the Worldstorm event, the origins of Grunge were further retooled. Owing his powers by careful genetic manipulations operated by the hidden Tabula Rasa group, and sharing somehow the soul of the previous iteration of the character, but none of the memories, Grunge lived his younger years as the stereotypical momma boy, sickly and nerdy in appearance and mannerism, and even more intelligent than Caitlin. However, when hitting adolescence, Grunge decided he was unhappy with his unpopular, bookish self, and decided to "reinvent himself", a new constant of his life, adopting a rebellious persona to distance himself from his overprotective mother, and covering his nerdish self with a more easy-going, frat-boy like persona. At that point, Tabula Rasa caught up with him, and he was kidnapped along with the other Gen-active boys. There Grunge, after helping in the escape, became a sort of big brother for his teammates, deeply caring for his new friends, and jokingly being the clown of the Gen¹³. His friendly and warm personality earned him the affections of his friends until he was forced to slay Kid Apollo of the Authoriteens in self-defense, which is something that leaves him in a deep state of depression until Caitlin and Roxy manage to remind him how he acted in self-defence alone, and he always managed to defend his friends. Returning to his old self, but noting how much he was now fearing "the ability to reinvent himself", followed his friends in the city, until the end of the world hit. There, he unwillingly absorbed the makeup of electric energies, becoming a discorporated being: in this guise, he's able to help his friends against a group of scarred humans, resentful against the capes that brought ruin and misery in their lives. Returning to corporeal form, he dismisses Rainmaker's hypothesis about Caitlin developing a Florence Nightingale Effect for the now blind Burnout: instead, he decides to crack the tension their leader is feeling by proposing that every one of his teammates should share their vision of a post-atomic future. True to his cheerful exterior, and his desire to protect his friends by making them comfortable, he describes a world of intelligent cockroaches and scantly-clad babes in which every day he merrily challenges the humanoid cockroaches in a skate competition for world's dominion, and getting the girls.
While on the surface seeming to be nothing more than a typical "frat boy" type, there is more to Grunge than he lets on. He also has a photographic memory but tends to keep this fact to himself for fear of being thought a nerd. Grunge is also an avid fan of comic books and Hong Kong Kung Fu movies and action films. He especially likes the films of Bruce Lee, Jackie Chan, and John Woo. A vocal video game lover with an excess of confidence in his gaming skills, Grunge has nonetheless been bested at fighting games by Freefall at least twice. Grunge is a fan of the bands White Zombie, The Smashing Pumpkins and the Foo Fighters.
After the Worldstorm reboot, however, the new Grunge exhibited an even more caring personality. A typical nerd in childhood, he becomes a true man able to reinvent himself even before discovering his powers by trying to change his personality in something more carefree, thus able to relate better with people of his own age. Overprotective and caring, Grunge now exhibits a big brother-like personality on his teammates, using his slacker surface to cheer his only true friends, the Gen13. Grunge now seems more aware of the deeper consequences of his action: after being forced to kill Kid Apollo to defend his friends, he spirals in depression until Rainmaker reassures him.
Grunge has the ability to molecularly bond with anything he comes in contact with. Once he bonds with an object he takes on its physical characteristics. For example, if he bonds with steel he gains increased strength and durability. His power is very similar to that possessed by the Marvel Comics character called the Absorbing Man. The limits of his absorption ability were never revealed. He at times was able to meld with the ground beneath him sinking his hands at one place and having them come up at another place. He has also absorbed the properties of sand, from sand in his boot. Instead of gaining the properties of a rock, as sand is just small stones, he gained a form not unlike Marvel's Sandman—a being made up of small grains which he can manipulate in a variety of ways.
The full extent of his powers was never fully addressed, with certain abilities seeming to appear out of nowhere and cease to be used soon after. It is revealed that he can actually assume the shape of objects he absorbs. While in the Gen¹³ 'Zine the creators established he was unable to absorb/copy the properties of other superhumans, he has on at least one occasion copied the physical abilities of Caitlin Fairchild. Another oddity that was never fully addressed was his extreme ability to heal himself. In the first mini series his arm can be seen being shattered, but shortly thereafter, it comes back together. He has been shot repeatedly and the bullets were rejected from his body. He seems to have a remarkable healing capacity, but a reason for this is never addressed. One theory is that he bonds with the embedded bullets, an ability shown when he was able to pass through a wall.
The current version is shown however able to absorb other superhumans' powers, and he does on a regular basis. He even claims to have a thing for gaining wings from flying superhumans. However, he cannot choose by himself what property he takes from the superhuman he's touching: while succeeding in gaining Nestling's wings, in one occasion he failed miserably in taking Caitlin's strength for himself. Instead, he absorbed her feminine and curvaceous appearance, being burdened with a large pair of breasts until he found another source of power for himself, an advanced suicide booth. Thus, he demonstrates how he's able to borrow even the abilities of complex machinery.
One time, he was captured in some kind of limbo. After hours of flying in the nowhere, he tried to absorbe the dimension itself, giving him god-like powers, however this power consumed too fast, bringing Grunge back to normal.
Aside from his powers, Grunge is also a skilled martial artist and has a photographic memory.In the alternate future of 2015, Grunge has become the business administrator for Spawn's demonic rule. Assisting him is Burnout. His female team members are now unwilling participants in Spawn's harem.
In the Gen¹³ animated movie, Grunge's voice was provided by Michael Balzary, better known as Flea from the rock band The Red Hot Chili Peppers.