Disney Toontown Online

Disney's Toontown Online, the first massively multiplayer online game designed specifically for kids and families, is an award-winning, kid-safe, endlessly evolving, and immersive 3-D online world.
In Toontown, players, as Toons, join forces to save the world from the invading robot Cogs - humorless business robots who are attempting to turn the colorful, happy world of Toontown into a corporate metropolis. Because Cogs can't take a joke, Toons use cartoon gags to crack them up!
Official Site: http://play.toontown.com/