Ernie is a minor character who first appears in episode 1 as one of the girl's classmates and makes his official appearance in episode 17.
Ernie hands out a special edition of the school newspaper about the Powerpuff Girls Z. However the kids in the class are upset about it because there aren't any good pictures in the article and they return the newspapers by throwing them at him. Bubbles supports his attempts to get a decent shot of her and the girls, even going as far as at one point ask him if he wants to take a picture of her while transformed (Which he rejects because he felt it was wrong to take a picture when the girls weren't fighting).
Later, he decides to go to New Townsville tower so he can spot the bad guys so he can get to the action in time to take a picture of the Powerpuff Girls Z. But then Mojo Jojo enters the tower with a new invention inspired by the pictures in the school newspaper's article about the PowerPuff Girls Z, which horrifies Ernie. Mojo ties Ernie up and keeps him as a hostage. As the PowerPuff girls come closer to the tower, Ernie tries to get out of the ropes before head butting Mojo and kicking him in an attempt to buy the girls some time. This works and the girls are able to defeat Mojo (While Ernie takes pictures, which the kids in class complain about again later) and take his weapon away.