The villainous monkey who becomes a giant in “Mr. Mojo’s Rising” is Mojo Jojo.
“Mr. Mojo’s Rising” is an episode of the original The Powerpuff Girls series centered on Mojo Jojo’s attempt to gain overwhelming power. As one of the girls’ most persistent enemies, he frequently uses inventions, scientific experiments, and elaborate plans to challenge Townsville’s defenders.
Mojo Jojo’s transformation history is central to the character. He began as Professor Utonium’s laboratory assistant, but the Chemical X accident altered him and helped trigger the girls’ creation. His intelligence and resentment then drive many of his schemes.
The title can cause confusion with other episodes involving enormous monsters or villains. The specific villain in this episode is Mojo Jojo, not Fuzzy Lumpkins or HIM. His species is a chimpanzee, while his name is the canonical character answer.