Mojo Jojo (voiced by Roger L. Jackson) is a supergenius monkey and the main antagonist of The PowerPuff Girls. Once he was known simply as Jojo, a lab assistant to Professor Utonium, and a troublemaker. One day when the Professor returned he decided to use sugar, spice, and everything nice to create three perfect little girls, as he was mixing the brew, Jojo pushed Utonium, causing to accidentally add an extra ingredient to the formula, Chemical X. The pot exploded, and caused a positive and negative event to occur. Jojo was exposed and his brain started to grow out his head and grow intelligent, and The Powerpuff Girls were born. Jojo left and found himself living as a Hobo on the streets, until learning about what the girls had done. When he saw the girls walking along the streets of Townsville, he made a plan to get back at them, and rule all of Earth. He rescued the girls from the Gang Green Gang, and asked them to help in creating his laboratory. Then he took all the monkeys from the city zoo, and enhanced their intellect. The plan was a success but soon backfired, and he decided to take measures into his own hands, he gave himself more Chemical X and became Mo' Mojo Jojo. However, his plan was completely shattered at the hands of The Powerpuff Girls and Professor Utonium, and most of his powers were diminished from Antidote X, and he was thrown in jail.
- Mojo Jojo will become Jeffrey's enemy in Jeffrey & Friends' Storm Adventures of The Powerpuff Girls Movie.