ToonClix was planned to be an expansion to grow the Clix Empire. It was a collectible miniatures game aimed more specifically at the 6-12 year old demographic, with nostalgia characters aimed at older and (presumably) existing Heroclix collectors. From the original article reporting on it from March 2006:

ToonClix will feature figures based on cartoon characters from the libraries of Warner Bros. (Looney Tunes), the Cartoon Network, Hanna Barbera, and the Kids’ WB. With only 36 figures in the first set ToonClix should be easy to collect and players will find enough to play a game in every pack. The goal of the game is to get your character to the highest state of happiness, and each figure will come with cards that can be used to create a diorama-like background.