The Beat-Alls were a team of supervillains comprising Mojo Jojo, HIM, Fuzzy Lumpkins and Princess Morbucks. As the name implies, they are a parody of the 1960s group The Beatles.
When the villains Mojo Jojo, HIM, Fuzzy Lumpkins and Princess Morbucks defeated the Powerpuff Girls one night, they discovered that together, they could be unstoppable. So together, they formed the Beat-Alls. The Powerpuff Girls were no match for the villains' teamwork attacks, so the girls used a chimp named Michelle (under the name of Moko Jono, a parody of John Lennon's widow, Yoko Ono) to get Mojo to fall in love so the team would have to disband.
The team disbanded because they couldn't stand Mojo and Moko.
They were a team only in "Meet the Beat-Alls", but they do reunite in the video game HIM and Seek.