The Gangreen Gang are a group of juvenile delinquents on the Powerpuff Girls cartoon, depicted as green-skinned from their unhealthy life-style. They are first villains Blossom, Bubbles, and Buttercup encountered, both as little girls walking home from school and as the first villains the girls fought as superheroes when the gang was seen stealing from a lady's grocery bags. In the episode "Buttercrush," Buttercup is shown as having a crush on the Gang's leader, Ace, which ends as soon as she sees that he was just using her to trap the other girls.
In the game, the Gang have given up their life of crime; Ace is now a rock star with a horde of groupies. They can be found at Marquee Row in the Downtown area of the map, next to the Marquee Row Infected Zone. Ace is now close friends with Buttercup after her battle with Mojo Jojo -- apparently her boyfriend and, under the name "Belladonna," a member of his band. He often talks about his Fusion counterpart in City Point, opining that Fusion Ace is giving him a bad name. During the mission "How to Date a Fusion," Ace is told by Lil' Arturo that Buttercup is helping Fuse. However, Ace later on reveals that Fusion Buttercup is responsible for framing Buttercup.
- The Gangreen Gang (especially Grubber) are a tribute to the works of cartoonist Ed Roth, particularly his "Rat Fink" character.
- The gang get their name from "gangrene," a serious type of infection that causes necrosis of the tissue, which commonly induces either amputation or death.