The original series premiered in 1998, whereas this series premiered in 2006. The girls were given an Age Lift from kindergarteners to Eight Graders in this version, but it's also the age the original girls would have been if they actually aged in real life.
At first, it seems confusing when the dub changed the names of the Gangreen Gang. Think about the original Powerpuff Girls episode where Ms. Keane gave the full names of every member except Ace. So when Ace says he's Bobby Green, he's actually saying his real name. Also the parents are weird, so Big Billy's mom could name him Big Boy and she called him Reggie in episode 14.
